Mass Extinction KTB: Maastrichtian-Paleocene

Environmental changes during the Cretaceous-Paleogene mass extinction and Paleocene-Eocene Thermal Maximum: Implications for the Anthropocene

TitleEnvironmental changes during the Cretaceous-Paleogene mass extinction and Paleocene-Eocene Thermal Maximum: Implications for the Anthropocene
Publication TypeJournal Article
Year of Publication2018
AuthorsKeller, G, Mateo, P, Punekar, J, Khozyem, H, Gertsch, B, Spangenberg, J, Bitchong, AMbabi, Adatte, T
JournalGondwana Research
Volume56
Pagination69–89
Date Publishedapr
Abstract

The Cretaceous-Paleogene boundary (KPB) mass extinction (~66.02 Ma) and the Paleocene-Eocene Thermal Maximum( PETM)(~55.8Ma) are two remarkable climatic and faunal events in Earth's history that have implications for the current Anthropocene global warming and rapid diversity loss. Here we evaluate these two events at the stratotype localities in Tunisia and Egypt based on climatewarming and environmental responses recorded in faunal and geochemical proxies. The KPBmass extinction is commonly attributed to the Chicxulub impact, but Deccan volcanism appears as amajor culprit.Newmercury analysis reveals thatmajor Deccan eruptions accelerated during the last 10 ky and reached the tipping point leading up to themass extinction. During the PETM, climatewarmed rapidly by ~5 °C,which is mainly attributed tomethane degassing from seafloor sediments during global warming linked to the North Atlantic Igneous Province (NAIP). Biological effectswere transient,marked by temporary absence ofmost planktic foraminifera due to ocean acidification followed by the return of the pre-PETM fauna and diversification. In contrast, the current rapid rise in atmospheric CO2 and climate warming are magnitudes faster than at the KPB or PETM events leading to predictions of a PETM-like response as best case scenario and rapidly approaching sixth mass extinction as worst-case scenario.  PDF

URLhttps://doi.org/10.1016/j.gr.2017.12.002
DOI10.1016/j.gr.2017.12.002

Upheavals during the Late Maastrichtian: Volcanism, climate and faunal events preceding the end-Cretaceous mass extinction

TitleUpheavals during the Late Maastrichtian: Volcanism, climate and faunal events preceding the end-Cretaceous mass extinction
Publication TypeJournal Article
Year of Publication2016
AuthorsKeller, G, Punekar, J, Mateo, P
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume441
Pagination137–151
Date Published01/2016
Abstract

The late Maastrichtian was a time of major climate, evolution and extinction extremes. Rapid climate warming of 2–3 °C in intermediate waters between 69.5 and 68 Ma (top C31r to base C30n) accompanied maximum evolutionary diversification (43% increase, zone CF5 to low CF4) in planktic foraminiferal history, followed immediately by a cluster of extinctions. During the last 250 ky of the Maastrichtian (C29r, zones CF2–CF1), rapid warming of 4 °C in intermediate waters and 8 °C on land resulted in high-stress environments ending in the mass extinction. The end-Cretaceous mass extinction is recorded in sediments between massive Deccan lava flows in India and attributed to SO2 and CO2 outgassing leading to ocean acidification. The early late Maastrichtian climate and faunal upheavals are not well known.

Here we document the faunal similarities of both events from the Indian Ocean through the Tethys and Gulf of Mexico. Results show that both extreme warm events are marked by high-stress environments characterized by decreased abundance and diversity of large specialized species and dwarfing, high abundance of low oxygen tolerant species, and disaster opportunist surface dweller Guembelitria blooms. The similarity in faunal response with the Deccan warming of C29r (CF2–CF1) suggests that volcanism was also responsible for the warming and faunal upheaval of the early late Maastrichtian. Major volcanic activity at this time included the onset of Deccan eruptions and Ninetyeast Ridge volcanism. The role of the Chicxulub impact appears to have been a contributing, rather than causal, factor in the mass extinction.   PDF

URLhttps://doi.org/10.1016/j.palaeo.2015.06.034
DOI10.1016/j.palaeo.2015.06.034

The Cretaceous-Tertiary boundary (KTB) transition in NE Brazil

TitleThe Cretaceous-Tertiary boundary (KTB) transition in NE Brazil
Publication TypeJournal Article
Year of Publication2013
AuthorsGertsch, B, Keller, G, Adatte, T, Berner, Z
JournalJournal of the Geological Society
Volume170
Issue2
Pagination249 - 262
Date Published01/2013
ISSN0016-7649
Abstract

The Cretaceous-Tertiary boundary (KTB) transition of the Poty Quarry near Recife, NE Brazil, is the most distant locality (7800 km from Yucatan) with reported Chicxulub impact-tsunami deposits, impact spherules and Ir anomaly. Investigations based on sedimentology, biostratigraphy, mineralogy, stable isotopes and elemental geochemistry failed to confirm these reports. The KTB is at an unconformity marked by erosion and bioturbation. Latest Maastrichtian planktic foraminiferal zones CF1 below the unconformity and early Danian zone P1a(1) above indicates a short hiatus with the KTB clay (zone P0), Ir anomaly and characteristic negative d13C excursion missing. Above the unconformity is an upward-fining micro-conglomerate with abundant reworked Cretaceous foraminifera, sub-angular phosphate clasts, calcitic and phosphatic spheroids along with an early Danian zone P1a(1) assemblage.

This deposit has previously been interpreted as impact-tsunami with impact spherules. However, the spheroids are common throughout the late Campanian-Maastrichtian and appear to be chamber infillings of the benthic foraminifer Dentalina alternata. The unconformity coincides with the latest Maastrichtian sea level fall, which is widely recognized globally. The upward fining micro-conglomerate is likely a gravity-flow deposit associated with the early Danian sea level rise. Two minor Ir anomalies (<0.7 ppb) in thin clay layers of zone Pla are unrelated to the Chicxulub impact. Although there is no evidence of the Chicxulub impact in the Poty Quarry, this section remains a very important distant example of the complex global environmental and sea level changes, including gravity flows, observed in KT sequences from North America through Mexico, Central America and the Caribbean and commonly misinterpreted as impact tsunami event.  PDF

URLhttp://jgs.geoscienceworld.org/cgi/doi/10.1144/jgs2012-029
DOI10.1144/jgs2012-029
Short TitleJournal of the Geological Society

The Cretaceous–Tertiary Mass Extinction, Chicxulub Impact, and Deccan Volcanism

TitleThe Cretaceous–Tertiary Mass Extinction, Chicxulub Impact, and Deccan Volcanism
Publication TypeBook Chapter
Year of Publication2012
AuthorsKeller, G
Book TitleEarth and Life
Pagination759 - 793
PublisherSpringer Netherlands
CityDordrecht
ISBN Number978-90-481-3427-4
KeywordsChicxulub impact, Cretaceous, Danian, deccan volcanism, Foraminifers, Maastrichtian, Mass extinctions, Paleogene
Abstract

After three decades of nearly unchallenged wisdom that a large impact (Chicxulub) on Yucatan caused the end-Cretaceous mass extinction, this theory is facing its most serious challenge from the Chicxulub impact itself, as based on evidence in Texas and Mexico and from Deccan volcanism in India. Data generated from over 150 Cretaceous–Tertiary (KT) boundary sequences to date make it clear that the long-held belief in the Chicxulub impact as the sole or even major contributor to the KT mass extinction is not supported by evidence. The stratigraphic position of the Chicxulub impact ejecta spherules in NE Mexico and Texas and the impact breccia within the crater on Yucatan demonstrate that this impact predates the KTB by about 300,000 years. Planktic foraminiferal and stable isotope analyses across the primary impact ejecta layer reveal that not a single species went extinct as a result of this impact and no significant environmental changes could be determined. The catastrophic effects of this impact have been vastly overestimated. In contrast, recent advances in Deccan volcanic studies indicate three volcanic phases with the smallest at 67.5 Ma, the main phase at the end of the Maastrichtian (C29r), and the third phase in the early Danian C29r/C29n transition (Chenet et al. 2007). The main phase of eruptions occurred rapidly, was marked by the longest lava flows spanning 1500 km across India, and ended coincident with the KT boundary. The KT mass extinction may have been caused by these rapid and massive Deccan lava and gas eruptions that account for ∼80% of the entire 3500 m thick Deccan lava pile.

URLhttp://link.springer.com/content/pdf/10.1007/978-90-481-3428-1_25
DOI10.1007/978-90-481-3428-110.1007/978-90-481-3428-1_25

Environmental changes during the Cetaceous-Paleogene mass extinction and Paleocene-Eocene thermal maximum: Implications for the Anthropocene

TitleEnvironmental changes during the Cetaceous-Paleogene mass extinction and Paleocene-Eocene thermal maximum: Implications for the Anthropocene
Publication TypeJournal Article
Year of Publication2017
AuthorsKeller, G, Mateo, P, Punekar, J, Khozyem, H, Gertsch, B, Spangenberg, J, Bitchong, A, Adatte, T
JournalGondwana Research
Date Publisheddec
Abstract

The Cretaceous-Paleogene boundary (KPB) mass extinction (~ 66.02 Ma) and the Paleocene-Eocene Thermal Maximum (PETM) (~ 55.8 Ma) are two remarkable climatic and faunal events in Earth's history that have implications for the current Anthropocene global warming and rapid diversity loss. Here we evaluate these two events at the stratotype localities in Tunisia and Egypt based on climate warming and environmental responses recorded in faunal and geochemical proxies. The KPB mass extinction is commonly attributed to the Chicxulub impact, but Deccan volcanism appears as a major culprit. New mercury analysis reveals that major Deccan eruptions accelerated during the last 10 ky and reached the tipping point leading up to the mass extinction. During the PETM, climate warmed rapidly by ~ 5 °C, which is mainly attributed to methane degassing from seafloor sediments during global warming linked to the North Atlantic Igneous Province (NAIP). Biological effects were transient, marked by temporary absence of most planktic foraminifera due to ocean acidification followed by the return of the pre-PETM fauna and diversification. In contrast, the current rapid rise in atmospheric CO2 and climate warming are magnitudes faster than at the KPB or PETM events leading to predictions of a PETM-like response as best case scenario and rapidly approaching sixth mass extinction as worst-case scenario.

URLhttps://doi.org/10.1016/j.gr.2017.12.002
DOI10.1016/j.gr.2017.12.002

Deccan volcanism linked to the Cretaceous-Tertiary boundary mass extinction: New evidence from ONGC wells in the Krishna-Godavari Basin

TitleDeccan volcanism linked to the Cretaceous-Tertiary boundary mass extinction: New evidence from ONGC wells in the Krishna-Godavari Basin
Publication TypeJournal Article
Year of Publication2011
AuthorsKeller, G, Bhowmick, PK, Upadhyay, H, Dave, A, Reddy, AN, Jaiprakash, BC, Adatte, T
JournalJournal of the Geological Society of India
Volume78
Issue5
Pagination399 - 428
Date PublishedJan-11-2011
ISSN0016-7622
Abstract

A scientific challenge is to assess the role of Deccan volcanism in the Cretaceous-Tertiary boundary (KTB) mass extinction. Here we report on the stratigraphy and biologic effects of Deccan volcanism in eleven deep wells from the Krishna-Godavari (K-G) Basin, Andhra Pradesh, India. In these wells, two phases of Deccan volcanism record the world’s largest and longest lava mega-flows interbedded in marine sediments in the K-G Basin about 1500 km from the main Deccan volcanic province. The main phase-2 eruptions (∼80% of total Deccan Traps) began in C29r and ended at or near the KTB, an interval that spans planktic foraminiferal zones CF1–CF2 and most of the nannofossil Micula prinsii zone, and is correlative with the rapid global warming and subsequent cooling near the end of the Maastrichtian. The mass extinction began in phase-2 preceding the first of four mega-flows. Planktic foraminifera suffered a 50% drop in species richness. Survivors suffered another 50% drop after the first mega-flow, leaving just 7 to 8 survivor species. No recovery occurred between the next three mega-flows and the mass extinction was complete with the last phase-2 mega-flow at the KTB. The mass extinction was likely the consequence of rapid and massive volcanic CO2 and SO2 gas emissions, leading to high continental weathering rates, global warming, cooling, acid rains, ocean acidification and a carbon crisis in the marine environment.

Deccan volcanism phase-3 began in the early Danian near the C29R/C29n boundary correlative with the planktic foraminiferal zone P1a/P1b boundary and accounts for ~14% of the total volume of Deccan eruptions, including four of Earth’s longest and largest mega-flows. No major faunal changes are observed in the intertrappeans of zone P1b, which suggests that environmental conditions remained tolerable, volcanic eruptions were less intense and/or separated by longer time intervals thus preventing runaway effects. Alternatively, early Danian assemblages evolved in adaptation to high-stress conditions in the aftermath of the mass extinction and therefore survived phase-3 volcanism. Full marine biotic recovery did not occur until after Deccan phase-3. These data suggest that the catastrophic effects of phase-2 Deccan volcanism upon the Cretaceous planktic foraminifera were a function of both the rapid and massive volcanic eruptions and the highly specialized faunal assemblages prone to extinction in a changing environment. Data from the K-G Basin indicates that Deccan phase-2 alone could have caused the KTB mass extinction and that impacts may have had secondary effects.

URLhttp://link.springer.com/article/10.1007%2Fs12594-011-0107-3
DOI10.1007/s12594-011-0107-3
Short TitleJ Geol Soc India

KT Mass Extinction: theories and controversies

TitleKT Mass Extinction: theories and controversies
Publication TypeWeb Article
Year of Publication2010
AuthorsKeller, G
Access DateMay 2010
PublisherGeoscientist Online
CityLondon
Abstract

Most mass extinctions that have afflicted life on Earth during the past 500 million years have occurred during times of major volcanic eruption and all were accompanied by major changes in climate, sea level and oxygenation levels in the ocean.  Among the five major mass extinctions, only the end-Cretaceous (KT) displays a close coincidence of four factors - an iridium anomaly (commonly assumed to represent an impact), an impact crater (Chicxulub), a large igneous province (the Deccan Traps) and major climate and sea level changes (Fig. 2). The KT mass extinction also differs in that it follows the longest period (145-65.5Ma) of low background extinction (Fig. 2). Throughout the Cretaceous, generic diversity had increased, accelerating during the Campanian and peaking during the late Maastrichtian, prior to the mass extinction.  PDF

URLhttp://www.geolsoc.org.uk/keller

Low-Diversity, Late Maastrichtian and Early Danian Planktic Foraminiferal Assemblages of the Eastern Tethys

TitleLow-Diversity, Late Maastrichtian and Early Danian Planktic Foraminiferal Assemblages of the Eastern Tethys
Publication TypeJournal Article
Year of Publication2004
AuthorsKeller, G
JournalThe Journal of Foraminiferal Research
Volume34
Issue1
Pagination49 - 73
Date PublishedJan-01-2004
ISSN0096-1191
Abstract

The eastern Tethys, from Israel to Egypt, experienced unusually adverse environmental conditions for planktic foraminifera during the last two million years of the Maastrichtian, as evident by very low species richness, blooms of opportunistic Guembelitria species in surface waters, dominance of low-oxygen-tolerant heterohelicids in subsurface waters, and near absence of deeper dwelling globotruncanids. Comparison of southern Israel (Mishor Rotem section) with central Egypt (Gebel Qreiya section) reveals that adverse conditions intensified towards the south with foraminiferal assemblages mimicking stress conditions of the early Danian, dominated (75– 90%) by Guembelitria blooms. Faunal assemblages indicate an expanded oxygen minimum and dysoxic zone throughout the region, though at the greater depths represented by localities of southern Israel, bottom waters remained aerobic. Primary productivity was extremely low, as indicated by stable isotopes and low total organic content in sediments. These adverse environmental conditions are likely related to the regional paleobathymetry of the tectonically active Syrian Arc that spans Syria to Egypt. The paleorelief of intra-shelf and intra-slope basins of the Syrian Arc, with their differential rates of subsidence and sedimentation, active folding and faulting, likely controlled the intensity of circulation, upwelling, watermass stratification and the extent of the oxygen minimum zone. The late Maastrichtian rapid climate and sea level changes exacerbated these conditions.  PDF

URLhttp://jfr.geoscienceworld.org/cgi/doi/10.2113/0340049
DOI10.2113/0340049
Short TitleThe Journal of Foraminiferal Research

Disaster opportunists Guembelitrinidae: index for environmental catastrophes

TitleDisaster opportunists Guembelitrinidae: index for environmental catastrophes
Publication TypeJournal Article
Year of Publication2004
AuthorsKeller, G, Pardo, A
JournalMarine Micropaleontology
Volume53
Issue1-2
Pagination83 - 116
Date PublishedJan-10-2004
ISSN03778398
KeywordsGuembelitria blooms; Volcanism; impacts; K–T; late Maastrichtian
Abstract

Blooms of the disaster opportunist Guembelitria species are proxies for environmental catastrophes, whether impact orvolcanism, leading to severe biotic stress crises that may range from temporary exclusion of ecological specialists and generalists to mass extinctions. During the late Maastrichtian and early Danian (zones P0 and Pla), Guembelitria blooms show global distributions, but with the largest blooms (40–80% Guembelitria) in low and middle latitudes and only minor blooms (10–20%) in high latitudes. Late Maastrichtian Guembelitria blooms are, so far, known from the Indian Ocean and eastern Tethys. The most intense Guembelitria blooms (>60% Guembelitria) occurred in shallow continental shelf areas, slope/shelf margins and volcanic provinces of the Indian Ocean. What these environments have in common is high nutrient influx (eutrophication) either from continental runoff, upwelling along continental margins or volcanic input. At times of biotic crises, Guembelitria blooms may have spread rapidly to the exclusion of most or all other species, much like today’s red tides, but with near global distributions. A simple model can explain the ecological succession and recovery phases that follow major biotic perturbations caused by impacts or volcanism that lead to exclusion of specialist and most generalist species. Within such highly stressed environments, Guembelitria is the only genus to thrive, and without competition, rapidly reproduce and exponentially increase their populations. When nutrients are depleted, populations rapidly decrease, leading to ecologic niches for other generalists and ecosystem recovery. Small low-O2-tolerant heterohelicid populations mark this second stage, followed by small trochospiral and planispiral species. With further environmental recovery, increasing competition, niche development and restoration of a well-stratified water mass, oligotrophic conditions are restored, opening habitats for the highly specialized and diverse species and a return to normal diverse assemblages. This ecological succession is observed in association with mantle plume volcanism in the Indian Ocean and eastern Tethys during the late Maastrichtian, and in association with the K–T impact and volcanism during the early Tertiary.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0377839804000672
DOI10.1016/j.marmicro.2004.04.012
Short TitleMarine Micropaleontology

Late Cretaceous to early Paleocene climate and sea-level fluctuations: the Tunisian record

TitleLate Cretaceous to early Paleocene climate and sea-level fluctuations: the Tunisian record
Publication TypeJournal Article
Year of Publication2002
AuthorsThierry, A, Keller, G, Stinnesbeck, W
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume2754
Start Page1
Keywordsbulk, clay minerals, climate fluctuations, geochemistry, K-T boundary, Maastrichtian, organic matter, sea-level, Tunisia, Upper Campanian
Abstract

Climate and sea-level fluctuations across the Cretaceous-Tertiary (K-T) transition in Tunisia were examined based on bulk rock and clay mineralogies, biostratigraphy and lithology in five sections (El Melah, El Kef, Elles, Ain Settara and Seldja) spanning from open marine to shallow inner neritic environments. Late Campanian to early Danian trends examined at El Kef and Elles indicate an increasingly more humid climate associated with sea-level fluctuations and increased detrital influx that culminates at the K-T transition. This long-term trend in increasing humidity and runoff in the Tethys region is associated with middle and high latitude cooling. Results of short-term changes across the K-T transition indicate a sea-level lowstand in the latest Maastrichtian about 25^100 ka below the K-T boundary with the regression marked by increased detrital influx at El Kef and Elles and a short hiatus at Ain Settara. A rising sea-level at the end of the Maastrichtian is expressed at Elles and El Kef by deposition of a foraminiferal packstone. A flooding surface and condensed sedimentation mark the K^T boundary clay which is rich in terrestrial organic matter. The P0- P1a transition is marked by a sea-level lowstand corresponding to a short hiatus at Ain Settara where most of P0 is missing and a period of non-deposition and erosion in the lower part of P1a (64.95 Ma). At Seldja, P0 and possibly the topmost part of CF1 are missing. These sea-level fluctuations are associated with maximum humidity. These data suggest that in Tunisia, long-term environmental stresses during the last 500 ka before the K-T boundary and continuing into the early Danian are primarily related to climate and sea-level fluctuations. Within this long-term climatic trend the pronounced warm and humid event within the latest Maastrichtian Zone CF1 may be linked to greenhouse conditions induced by Deccan volcanism. The absence of any significant clay mineral variations at or near the K-T boundary and Ir anomaly suggests that the bolide impact had a relatively incidental short-term effect on climate in the Tethys region.   PDF

Paleoenvironment across the Cretaceous-Tertiary transition in eastern Bulgaria

TitlePaleoenvironment across the Cretaceous-Tertiary transition in eastern Bulgaria
Publication TypeBook Chapter
Year of Publication2002
AuthorsAdatte, T, Keller, G, Burns, S, Stoykova, KH, Ivanov, MI, Vangelov, D, Kramar, U, Stüben, D
Book TitleCatastrophic Events and Mass Extinctions: Impacts and Beyond: Boulder, Colorado
PublisherGeological Society of America Special Paper 356
CityBoulder
Abstract

The Cretaceous-Tertiary (K-T) transition in eastern Bulgaria (Bjala) was analyzed in terms of lithology, mineralogy, stable isotopes, trace elements, and planktic foraminifera. The sequence represents a boreal-Tethyan transitional setting, spans from the last 300 k.y. of the Maastrichtian (zone CF1) through the early Danian (zones P0-Plc), and contains several short hiatuses. It differs from low-latitude Tethyan sequences primarily by lower diversity assemblages, pre-K-T faunal changes, a reduced K-T δ13C shift, and the presence of two clay layers with platinum group element anomalies. The first clay layer marks the K-T boundary impact event, as indicated by an iridium anomaly (6.1 ppb), the mass extinction of tropical and subtropical planktic foraminifera, and cooling. The second clay layer is stratigraphically within the upper Parvularugoglobigerina eugubina (Pla) zone and contains a small Ir enrichment (0.22 ppb), a major Pd enrichment (1.34 ppb), and anomalies in Ru (0.30 ppb) and Rh (0.13 ppb) that suggest a volcanic source.  PDF

Guembelitria-dominated late Maastrichtian planktic foraminiferal assemblages mimic early Danian in central Egypt

TitleGuembelitria-dominated late Maastrichtian planktic foraminiferal assemblages mimic early Danian in central Egypt
Publication TypeJournal Article
Year of Publication2002
AuthorsKeller, G
JournalMarine Micropaleontology
Volume47
Issue1-2
Pagination71 - 99
Date PublishedJan-01-2003
ISSN03778398
Abstract

During the late Maastrichtian (66.8-65.5 Ma) the Asyut Basin in central Egypt experienced a breakdown of the surface to bottom gradient of the 13C/12C ratio with planktic N13C values 0.2-0.8x lighter than benthic values. Planktic foraminiferal species diversity was reduced by more than 50%, with assemblages dominated (60-90%) by the opportunistic blooms of the disaster species Guembelitria cretacea, which mimic the early Danian. The prolonged breakdown in productivity occurred during a time of tectonic activity and increased terrestrial runoff that may have resulted in highly eutrophic waters, coupled with a sea-level regression (65.5 Ma) that led to restricted circulation. Increased productivity during the short climate warming between 65.4 and 65.2 Ma is associated with increased species diversity, abundant rugoglobigerinids and common heterohelicids. At the end of the Maastrichtian, decreased productivity coincided with the K/T impact and mass extinction, followed by characteristically early Danian low diversity assemblages. The similarity of the late Maastrichtian and post-K/T impact Guembelitria-dominated assemblages reveals that the planktic foraminiferal response to the K/T catastrophe was not unique, but followed a predictable pattern of response to severe environmental perturbations.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0377839802001160
DOI10.1016/S0377-8398(02)00116-0
Short TitleMarine Micropaleontology

Paleoecology of the Cretaceous–Tertiary mass extinction in planktonic foraminifera

TitlePaleoecology of the Cretaceous–Tertiary mass extinction in planktonic foraminifera
Publication TypeJournal Article
Year of Publication2002
AuthorsKeller, G, Adatte, T, Stinnesbeck, W, Luciani, V, Karoui-Yaakoub, N, Zaghbib-Turki, D
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume178
Issue3-4
Pagination257 - 297
Date PublishedJan-02-2002
ISSN00310182
KeywordsTunisia; paleoecology; K-T planktonic foraminifera
Abstract

Paleobiogeographic patterns of the Cretaceous^Tertiary (K-T) mass extinction in planktonic foraminifera in Tunisia, spanning environments from open marine upper bathyal, to shelf and shallow marginal settings, indicate a surprisingly selective and environmentally mediated mass extinction. This selectivity is apparent in all of the environmental proxies used to evaluate the mass extinction, including species richness, ecological generalists, ecological specialists, surface and subsurface dwellers, whether based on the number of species or the relative percent abundances of species. The following conclusions can be reached for shallow to deep environments: about three quarters of the species disappeared at or near the K-T boundary and only ecological generalists able to tolerate wide variations in temperature, nutrients, salinity and oxygen survived. Among the ecological generalists (heterohelicids, guembelitrids, hedbergellids and globigerinellids), only surface dwellers survived. Ecological generalists which largely consisted of two morphogroups of opportunistic biserial and triserial species also suffered selectively. Biserials thrived during the latest Maastrichtian in well stratified open marine settings and dramatically declined in relative abundances in the early Danian. Triserials thrived only in shallow marginal marine environments, or similarly stressed ecosystems, during the latest Maastrichtian, but dominated both open marine and restricted marginal settings in the early Danian. This highly selective mass extinction pattern reflects dramatic changes in temperature, salinity, oxygen and nutrients across the K-T boundary in the low latitude Tethys ocean which appear to be the result of both long-term environmental changes (e.g., climate, sea level, volcanism) and short-term effects (bolide impact). PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0031018201003996
DOI10.1016/S0031-0182(01)00399-6
Short TitlePalaeogeography, Palaeoclimatology, Palaeoecology

The Cretaceous–Tertiary (K–T) mass extinction in planktic foraminifera at Elles I and El Melah, Tunisia

TitleThe Cretaceous–Tertiary (K–T) mass extinction in planktic foraminifera at Elles I and El Melah, Tunisia
Publication TypeJournal Article
Year of Publication2002
AuthorsKaroui-Yaakoub, N, Zaghbib-Turki, D, Keller, G
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume178
Pagination233–255
Date Publishedfeb
Abstract

Planktic foraminiferal faunas across the K-T transition at Elles and El Melah in northwestern and northeastern Tunisia, respectively, reveal patterns of species extinctions and species survivorship similar to those found at the El Kef stratotype and the Ain Settara sections. Slightly more than 2/3 of the species disappeared at or before the K-T boundary event and slightly less than 1/3 survived into the Danian where most disappeared sequentially within zone P1a (Parvularugoglobigerina eugubina) Relative species abundance patterns reveal that the 13-16 K-T survivors dominated (80%) the assemblages in the latest Maastrichtian, whereas the K-T extinct species were rare and totaled less than 20% of the total assemblages.

The K-T survivors are generally small with little surface ornamentation and geographically widespread from low tohigh latitudes. In contrast, K-T extinct species are large, highly ornamented and geographically restricted to low latitudes. This indicates that the K-T mass extinction was selective, rather than random, and predominantly affected the less robust tropical species. With the exception of the opportunistic Guembelitria species which dominate the early Danian, most K-T survivor species suffered severely as is evident by the decreased species populations after the K-Tevent. Their eventual demise appears to have been related to post-K-T environmental changes and competition fromevolving Tertiary species. These results reveal a complex mass extinction pattern that in addition to the K-T impactevent is keyed to long-term environmental changes preceding and following this event.  PDF

URLhttps://doi.org/10.1016/s0031-0182(01)00398-4
DOI10.1016/s0031-0182(01)00398-4

The Cretaceous–Tertiary (K/T) boundary transition at Coxquihui, state of Veracruz, Mexico: evidence for an early Danian impact event?

TitleThe Cretaceous–Tertiary (K/T) boundary transition at Coxquihui, state of Veracruz, Mexico: evidence for an early Danian impact event?
Publication TypeJournal Article
Year of Publication2002
AuthorsStinnesbeck, W, Keller, G, Schulte, P, üben, D, BERNER, ZSOLT, Kramar, U, é Lopez-Oliva, G
JournalJournal of South American Earth Sciences
Volume15
Issue5
Pagination497 - 509
Date PublishedJan-10-2002
ISSN08959811
KeywordsCretaceous–Tertiary boundary; Spherule-rich deposits; Early Danian impact event
Abstract

The Cretaceous–Tertiary (K/T) transition at Coxquihui, State of Veracruz, Mexico, differs from all other Mexican sections by the presence of two spherule-rich layers interbedded with pelagic marls, but lacking the characteristic siliciclastic deposit. A 1-cm-thick spherule layer is located at or near the K/T boundary and contains a small Ir enrichment of 0.2 ng/g (background values <0.1 ng/g). The precise stratigraphic position of this spherule layer with respect to the K/T boundary is uncertain due to a hiatus that spans from to the lower Parvularugoglobigerina eugubina Zone (Pla) to the upper part of the latest Maastrichtian Plummerita hantkeninoides Zone. A 20-cm-thick marl layer separates the first spherule layer from a 60-cm-thick second spherule layer, which is also within Zone Pla. An Ir enrichment of 0.5 ng/g is present in the overlying 10-cm-thick marl layer. The stratigraphic positions of these two spherule layers and Ir enrichments are strikingly similar to those found at two other localities, Beloc in Haiti and Caribe in Guatemala, and suggest the possibility of an early Danian impact event.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0895981102000792
DOI10.1016/S0895-9811(02)00079-2
Short TitleJournal of South American Earth Sciences

Trace elements, stable isotopes, and clay mineralogy of the Elles II K–T boundary section in Tunisia: indications for sea level fluctuations and primary productivity

TitleTrace elements, stable isotopes, and clay mineralogy of the Elles II K–T boundary section in Tunisia: indications for sea level fluctuations and primary productivity
Publication TypeJournal Article
Year of Publication2002
AuthorsStüben, D, Kramar, U, Berner, Z, Stinnesbeck, W, Keller, G, Adatte, T
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume178
Issue3-4
Pagination321 - 345
Date PublishedJan-02-2002
ISSN00310182
Abstract

Trace elements and stable isotopes in bulk rocks and foraminifera, bulk rock and clay mineral compositions, are used as palaeoproxies to evaluate sea level fluctuations, climatic changes and variations in primary productivity across the K-T transition at Elles II in Tunisia from 1 m (~33 kyr) below to 1 m (~70 kyr) above the K-T boundary. Results on clay minerals, major and trace elements, stable isotopes in bulk rock samples (e.g. Ca, Cu, Zn, Rb, Sr, Zr, Ba, δ13C and δ18O), and in foraminifera (Sr/Ca, N13C, N18O) indicate that the latest Maastrichtian (last~33 kyr) in Tunisia was marked by a relatively warm, but humid climate and a rising sea level. The transgressive surface is marked by deposition of a foraminiferal packstone just below the K-T boundary followed by maximum flooding across the K-T boundary (red layer and black clay layer). Humid warm conditions accompanied the maximum flooding, along with increased total organic carbon values and rapidly decreasing primary productivity. At the K-T boundary, an impact event (Ir anomaly, Ni-rich spinels, spherules) exacerbated already stressed environmental conditions leading to the mass extinction of tropical planktic foraminifera. Increasingly more humid conditions prevailed within the lowermost Danian Zone P0 (~50 kyr) culminating in a sea level lowstand near the top of P0. A slow recovery of the ecosystem in Zone P1a coincided with a rising sea level and gradually less humid climatic conditions.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0031018201004011
DOI10.1016/S0031-0182(01)00401-1
Short TitlePalaeogeography, Palaeoclimatology, Palaeoecology

High stress late Maastrichtian paleoenvironment: inference from planktonic foraminifera in Tunisia

TitleHigh stress late Maastrichtian paleoenvironment: inference from planktonic foraminifera in Tunisia
Publication TypeJournal Article
Year of Publication2002
AuthorsAbramovich, S, Keller, G
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume178
Issue3-4
Pagination145 - 164
Date PublishedJan-02-2002
ISSN00310182
Abstract

High resolution (~5-10 kyr) planktonic foraminiferal analysis at Elles, Tunisia, reveals major changes in the structure of the Tethyan marine ecosystem during the upper Maastrichtian. During the first 1.5 Myr of the late Maastrichtian (68.3-66.8 Ma) relatively stable environmental conditions and cool temperatures are indicated by diverse planktonic foraminiferal populations with abundant intermediate and surface dwellers. A progressive cooling trend between ~66.8-65.45 Ma resulted in the decline of globotruncanid species (intermediate dwellers). This group experienced a further decline at the climax of a rapid warm event about 300 kyr before the K-T boundary. At the same time relative abundances of long ranging dominant species fluctuated considerably reflecting the high stress environmental conditions. Times of critical high stress environments during the late Maastrichtian, and particularly at the K-T boundary, are indicated by low species diversity and blooms of the opportunistic genus Guembelitria at warm-cool transition intervals. During the last 100 kyr of the Maastrichtian rapid cooling is associated with accelerated species extinctions followed by the extinction of all tropical and subtropical species at the K-T boundary.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0031018201003947
DOI10.1016/S0031-0182(01)00394-7
Short TitlePalaeogeography, Palaeoclimatology, Palaeoecology

Are Ir anomalies sufficient and unique indicators for cosmic events?

TitleAre Ir anomalies sufficient and unique indicators for cosmic events?
Publication TypeJournal Article
Year of Publication2001
AuthorsKramar, U, üben, D, Berner, Z, Stinnesbeck, W, Philipp, H, Keller, G
JournalPlanetary and Space Science
Volume49
Issue8
Pagination831 - 837
Date PublishedJan-07-2001
ISSN00320633
Abstract

Ir anomalies are often considered unique indicators for cosmic events. The present paper compares the contents and patterns of platinum group element (PGE) anomalies of magmatic and sedimentary origins with similar anomalies found in the Cretaceous–Tertiary (K/T) boundary impact clay and other PGE enriched layers across the K/T boundary and early Danian (Parvularugoglobigerina eugubina zone) at Beloc, Haiti. This analysis demonstrates that PGE patterns provide more conclusive evidence for the reconstruction of paleoevents than that can be achieved by Ir content alone.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0032063301000368
DOI10.1016/S0032-0633(01)00036-8
Short TitlePlanetary and Space Science

Maastrichtian to Paleocene depositional environment of the Dakhla Formation, Western Desert, Egypt: sedimentology, mineralogy, and integrated micro- and macrofossil biostratigraphies

TitleMaastrichtian to Paleocene depositional environment of the Dakhla Formation, Western Desert, Egypt: sedimentology, mineralogy, and integrated micro- and macrofossil biostratigraphies
Publication TypeJournal Article
Year of Publication2001
AuthorsTantawy, AA, Keller, G, Adatte, T, Stinnesbeck, W, Kassab, A, Schulte, P
JournalCretaceous Research
Volume22
Issue6
Pagination795 - 827
Date PublishedJan-12-2001
ISSN01956671
Abstract

Integrated sedimentology, mineralogy, geochemistry, and microfossil and macrofossil biostratigraphies of the Maastrichtian– early Paleocene Dakhla Formation of the Western Desert, Egypt, provide improved age resolution, information on the cyclic nature of sediment deposition, and the reconstruction of depositional environments. Age control based on integrated biostratigraphies of planktic foraminifera, calcareous nannofossils and macrofossils yields the following ages for stratigraphic and lithologic sequences. The contact between the Duwi and Dakhla formations marks the Campanian/Maastrichtian boundary (zone CF8a/b boundary) and is dated at about 71 Ma. The age of the Dakhla Formation is estimated to span from 71 Ma at the base to about 63 Ma at the top (zones CF8a–Plc). The Cretaceous/Tertiary (K/T) boundary is within the upper unit of the Kharga Shale Member and marked by a hiatus that spans from 64.5 Ma in the lower Paleocene (base Plc) to at least 65.5 Ma (base CF2, base M. prinsii zones) in the upper Maastrichtian at Gebel Gifata, the type locality of the Dakhla Formation. As a result, the Bir Abu Minqar horizon, deposited between about 64.2 and 64.5 Ma (Plc(l) zone), directly overlies the K/T boundary hiatus. Major hiatuses also span the late Maastrichtian–early Paleocene in sections to the northwest (c. 61.2–65.5 Ma at North El Qasr, c. 61.2–69 Ma at Bir Abu Minqar and c. 61.2–65.5 Ma at Farafra), and reflect increased tectonic activity.

During the Maastrichtian–early Paleocene a shallow sea covered the Western Desert of Egypt and the clastic sediment source was derived primarily from tectonic activity of the Gilf El Kebir spur to the southwest of Dakhla and the Bahariya arch. Uplift in the region resulted in major hiatuses in the late Maastrichtian–early Paleocene with increased erosion to the southwest. The area was located near the palaeoequator and experienced warm, wet, tropical to subtropical conditions characterized by low seasonality contrasts and predominantly chemical weathering (high kaolinite and smectite). A change towards perennially more humid conditions with enhanced runoff (increased kaolinite) occurred towards the end of the Maastrichtian and in the early Paleocene with shallow seas fringed by Nypa palm mangroves. Sediment deposition was predominantly cyclic, consisting of alternating sandstone/shale cycles with unfossiliferous shales deposited during sea-level highstands in inner neritic to lagoonal environments characterized by euryhaline, dysaerobic or low oxygen conditions. Fossiliferous calcareous sandstone layers were deposited in well-oxygenated shallow waters during sea-level lowstand periods.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0195667101902915
DOI10.1006/cres.2001.0291
Short TitleCretaceous Research

Iridium and the K/T boundary at El Caribe, Guatemala

TitleIridium and the K/T boundary at El Caribe, Guatemala
Publication TypeJournal Article
Year of Publication2000
AuthorsKeller, G, Stinnesbeck, W
JournalInternational Journal of Earth Sciences
Volume88
Issue4
Pagination840 - 843
Date PublishedOct-03-2001
ISSN1437-3254
Abstract

At El Caribe, Guatemala, we reported the presence of up to 10±15% altered glass spherules near the top of the breccia, which is located stratigraphically near the K/T boundary, and linked these to the Chicxulub impact (Stinnesbeck et al. l997). We also noted that analyses of Ir by R. Rocchia failed to show anomalous concentrations at the top of the breccia (Stinnesbeck et al. l997, p. 703). In this short note we amend this statement and elaborate as to the actual Ir values reported by Rocchia and the precise stratigraphic position of the Ir analyses made by him in our section as well as the section collected by Fourcade et al. (l998). We then place these findings within the context of new geological studies in Haiti and Guatemala.  PDF

URLhttp://link.springer.com/10.1007/s005310050310http://www.springerlink.com/index/pdf/10.1007/s005310050310
DOI10.1007/s005310050310
Short TitleInternational Journal of Earth Sciences

High Resolution Carbon and Oxygen Isotope Profiles of Foraminifera and tha Ca-Normalized Sr Curve from Late Maastrichtian across the KTB at Elles, Tunisia.

TitleHigh Resolution Carbon and Oxygen Isotope Profiles of Foraminifera and tha Ca-Normalized Sr Curve from Late Maastrichtian across the KTB at Elles, Tunisia.
Publication TypeJournal Article
Year of Publication2000
AuthorsD, S, Kramar, U, BERNER, ZSOLT, M.A., L, Stinnesbeck, W, Adatte, T
JournalIsotopes in Environmental and Health Studies
Volume36
Pagination393-396
Date Published01
Abstract

Due to the discussion of global catastrophic events at the Cretaceous-Tertiary (KT) boundary based on various reason e.g. [1], [2], [3], [4] and to controversial discussion on the faunal extinction based on high-resolution biostratigraphic investigations e.g. [5], [6] studies to investigate the climate record of the last million years of the Maastrichtian became important.

Stable isotope studies of deep sea sites in the Pacific and South Atlantic reveal a terminal Cretaceous warm event as a distinct 2-3o C warming of intermediate waters across latitudes and a 2-3o C warming in surface waters in middle and high southern latitudes [7]. The well documented long-term cooling trend that characterizes the late Cretaceous was terminated by a short-term warming followed by a rapid cooling near the end of the Maastrichtian 100-200 kyr before the KT boundary [8], [9].

However, different sample resolution, condensed or erosional sedimentation, short-term hiatuses, bioturbation, diagenetic alteration etc. makes a highresolution chemostratigraphy necessary to determine the nature of this terminal Cretaceous warm event and the cooling shortly below the KT boundary.

Climate and depositional variations during the last 570 000 years of Late Maastrichtian are presented for a 26 m long ELLES section on the base of a highresolution chemostratigraphy (d13 C, d18 O isotopes andCa-normalized Sr gradients).  PDF

Variability in Late Cretaceous climate and deep waters: evidence from stable isotopes

TitleVariability in Late Cretaceous climate and deep waters: evidence from stable isotopes
Publication TypeJournal Article
Year of Publication1999
AuthorsLi, L, Keller, G
JournalMarine Geology
Volume161
Issue2-4
Pagination171 - 190
Date PublishedJan-10-1999
ISSN00253227
KeywordsMaastrichtian; Stable isotopes; Climate; Deep-water
Abstract

Strong climatic and temperature fluctuations mark the Late Campanian and Maastrichtian as indicated by stable isotope records from the equatorial Pacific (Site 463) and middle and high latitude South Atlantic (Sites 525, 689 and 690). The first major global cooling decreased intermediate water temperatures (IWT) by 5–6°C between 73–70 Ma. At the same time, sea surface temperature (SST) decreased by 4–5°C in middle and high latitudes. Intermediate waters (IW) temporarily warmed by 2°C in low and middle latitudes between 70–68.5 Ma. Global cooling resumed between 68.5–65.5 Ma when IWT decreased by 3–4°C and SST by 5°C in middle latitudes. About 450 ka before the Cretaceous–Tertiary boundary rapid global warming increased IWT and SST by 3–4°C, though SST in the tropics changed little. During the last 200 ka of the Maastrichtian, climate cooled rapidly with IWT and SST decreasing by 2–3°C. During the global cooling at 71–70 Ma and possibly at 67–65.5 Ma, the sources of cold intermediate waters in the equatorial Pacific, Indo-Pacific and South Atlantic were derived from the high latitude North Pacific. In contrast, during the global climate warming between 65.2–65.4 Ma, the middle latitude South Atlantic was closest to the source of IW production and implies that the low latitude Tethys played a major role in global climate change. Climate changes, sea-level fluctuations and associated restricted seaways appear to be the most likely mechanisms for the alternating sources of IW production.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S002532279900078X
DOI10.1016/S0025-3227(99)00078-X
Short TitleMarine Geology

The Late Campanian and Maastrichtian in northwestern Tunisia: palaeoenvironmental inferences from lithology, macrofauna and benthic foraminifera

TitleThe Late Campanian and Maastrichtian in northwestern Tunisia: palaeoenvironmental inferences from lithology, macrofauna and benthic foraminifera
Publication TypeJournal Article
Year of Publication1999
AuthorsLi, L, Keller, G, Stinnesbeck, W
JournalCretaceous Research
Volume20
Pagination231–252
Date Publishedapr
Abstract

Late Campanian through Maastrichtian sea-level changes are examined based on lithology, macrofossils and benthic foraminifera at the Elles and El Kef sections in Tunisia. Six major sea-level regressions are identified during the late Campanian (74.4–74.2 Ma, 74.0–72.5 Ma), the Campanian-Maastrichtian transition (72.2–70.3 Ma), early Maastrichtian (69.6–69.3 Ma, 68.9–68.3 Ma), and late Maastrichtian (∼65.5 Ma). Correlation of the Maastrichtian sea-level regressions with the oxygen isotope record of DSDP Site 525 in the middle latitude South Atlantic reveals that they coincide with episodes of high latitude cooling and appear to be of eustatic origin.   PDF

URLhttps://doi.org/10.1006/cres.1999.0148
DOI10.1006/cres.1999.0148

Aspectos paleoceanográficos y paleoecológicos del límite Cretácico/Terciario en la Península de Mangyshlak (Kazakstan): inferencias a partir de foraminíferos planctónicos.

TitleAspectos paleoceanográficos y paleoecológicos del límite Cretácico/Terciario en la Península de Mangyshlak (Kazakstan): inferencias a partir de foraminíferos planctónicos.
Publication TypeJournal Article
Year of Publication1999
AuthorsPardo, A, Gerta, K
JournalRev. Esp. Micropal
Volume31
Issue2
Pagination265-278
Abstract

Comparison of planktic foraminiferal assemblages from sections at Koshak and Kyzylsai (boreal Paratethys) allows an analysis of the biotic crisis occurred during the Cretaceous-Tertiary transition (K-T) in the Mangyslak Peninsula. Foraminiferal assemblages in both sections are typically oligotaxic, with low species richness and a single dominant species (Chiloguembelina waiparaensis), through the late Maastrchtian and early Danian. In the latest Maastrichtian in the Koshak and Kyzylsai sections, a group of exotic planktic foraminifera from low latitudes appears in the assamblage, suggesting seawater warming and a rising sea level. These are tropical-subtropical, large and ornate planktic foraminifera that account for less than 25% of the assemblage and they disappear before or at the K/T boundary in both sections. The species that survive the K/T boundary are the endemic, small, cosmopolitan opportunists, they are biserial, triserial and trochospiral taxa of simple morphologies, mostly surface dwellers or able to tolerate low oxygen conditions. These survivor taxa account for more than 75% of the assemblage. Decreased primary productivity and oxygen during the latest Maastrichtian are suggested as the main factors for the K/T biotic crisis and its ecologic selectivity in the low latitudes. However, in high latitudes environmental conditions (including productivity) changed little and this resulted in a less catastrophic K/T boundary biotic event.

URLhttp://www.igme.es/Publicaciones/revistaMicro/vol32/rem29apardo.htm

Paleoenvironmental changes across the Cretaceous–Tertiary boundary at Koshak, Kazakhstan, based on planktic foraminifera and clay mineralogy

TitlePaleoenvironmental changes across the Cretaceous–Tertiary boundary at Koshak, Kazakhstan, based on planktic foraminifera and clay mineralogy
Publication TypeJournal Article
Year of Publication1999
AuthorsPardo, A, Adatte, T, Keller, G, Oberhänsli, H
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume154
Pagination247–273
Date Publishednov
Abstract

The Koshak section of the Mangyshlack Peninsula, Kazakhstan, is one of the most complete Cretaceous–Tertiary (K–T) transitions known from the boreal Paratethys. Cretaceous species richness is low (11 to 13 species), except for a peak of 20 species near the K/T boundary in the uppermost Maastrichtian (top 50 cm) that represents the temporary incursion of low-latitude taxa. This maximum species richness occurred during climatic warming associated with increased humidity, as suggested by clay mineral analyses. Biofacies analysis suggests external platform conditions at this time, followed by a more humid climate, a sea-level transgression, and deepening basinal facies in the lower Danian Subzone P1a. Shallower platform conditions resumed in Danian Subzones P1b and P1c, accompanied by a cooler and probably more arid climate. No abrupt mass extinction occurred at the Koshak K/T boundary which is marked by an Ir anomaly, a clay layer and the first appearance of Tertiary planktic foraminifera. The influx of lower-latitude species ends at or before the K/T boundary, whereas the majority of the indigenous Cretaceous assemblage survived into the Danian. These data suggest that long-term climatic changes may have been the principal factors in the progressive demise of the Cretaceous planktic foraminifera in the eastern boreal Paratethys.   PDF

URLhttps://doi.org/10.1016/s0031-0182(99)00114-5
DOI10.1016/s0031-0182(99)00114-5

Diversification and extinction in Campanian-Maastrichtian planktic foraminifera of northwestern Tunisia

TitleDiversification and extinction in Campanian-Maastrichtian planktic foraminifera of northwestern Tunisia
Publication TypeJournal Article
Year of Publication1998
AuthorsLi, L, Keller, G
JournalEclogae Geologicae Helvetiae
Volume91
Issue1
Start Page75 - 102
Abstract

Investigation of Campanian-Maastrichtian planktic foraminifera in north Tunisia reveals that the late Maastrichtian not only ends with a mass extinction, but also attains maximum species diversity during theirevolutionary history. Maximum species diversity is reached during global cooling in the early late Maastrichtian over a 600 kyr interval (69.1-69.7 Ma) when species richness nearly doubled with the evolution of many rugoglobigerinids and globotruncanids. No species extinctions occur at this time and there is little change in the relative abundanceof existing species, whereas new species did not evolve into numerically large populations during the succeeding late Maastrichtian. This suggests that species originations did not result in major competition and that the early-late Maastrichtian climatic cooling may have resulted in increased habitats and nutrient supply for marine plankton. The onset of the permanent decline in Cretaceous species richness began at65.9 Ma and accelerated during the last 50-100 kyr of the Maastrichtian, culminating in the mass extinction of all tropical and subtropicaltaxa at the end of the Maastrichtian. Climate changes appear to be responsible for both the rapid evolutionary activity in the early late Maastrichtian, as well as the gradual decline in species richness near the end of the Maastrichtian, although the additional stress imposed on the ecosystem by a bolide impact is the likely cause for the final demise of the tropical and subtropical fauna at the K-T boundary.

URLhttp://serials.unibo.it/cgi-ser/start/it/spogli/df-s.tcl?prog_art=5567963&language=ITALIANO&view=articoli

Abrupt deep-sea warming at the end of the Cretaceous

TitleAbrupt deep-sea warming at the end of the Cretaceous
Publication TypeJournal Article
Year of Publication1998
AuthorsLi, L, Keller, G
JournalGeology
Volume26
Pagination995-998
Abstract

Climatic and oceanographic variations during the last 2 m.y. of the Maastrichtian inferred from high-resolution (10 k.y.) stable isotope analysis of the mid-latitude South Atlantic Deep Sea Drilling Project Site 525 reveal a major warm pulse followed by rapid cooling prior to the Cretaceous-Tertiary boundary. Between 66.85 and 65.52 Ma, cool but fluctuating temperatures average 9.9 and 15.4 °C in intermediate and surface waters, respectively. This interval is followed by an abrupt short-term warming between 65.45 and 65.11 Ma, which increased temperatures by 2–3 °C in intermediate waters, and decreased the vertical thermal gradient to an average of 2.7 °C. This warm pulse may be linked to increased atmospheric pCO2, increased poleward heat transport, and the switch of an intermediate water source from high to low-middle latitudes. During the last 100 k.y. of the Maastrichtian, intermediate and surface temperatures decreased by an average of 2.1 and 1.4 °C, respectively, compared to the maximum temperature between 65.32 and 65.24 Ma.  PDF

URLhttp://geology.gsapubs.org/content/26/11/995.abstract
DOI10.1130/0091-7613(1998)026<0995:ADSWAT>2.3.CO;2

Maastrichtian climate, productivity and faunal turnovers in planktic foraminifera in South Atlantic DSDP sites 525A and 21

TitleMaastrichtian climate, productivity and faunal turnovers in planktic foraminifera in South Atlantic DSDP sites 525A and 21
Publication TypeJournal Article
Year of Publication1998
AuthorsLi, L, Keller, G
JournalMarine Micropaleontology
Volume33
Issue1-2
Pagination55 - 86
Date PublishedJan-02-1998
ISSN03778398
Abstract

Stratigraphic, faunal and isotopic analyses of the Maastrichtian at DSDP sites 525A and 21 in the South Atlantic reveal a planktic foraminiferal fauna characterized by two major events, an early late Maastrichtian diversification and end-Maastrichtian mass extinction. Both events are accompanied by major changes in climate and productivity. The diversification event which occurred in two steps between 70.5 and 69.1 Ma increased species richness by a total of 43% and coincided with the onset of major cooling in surface and bottom waters and increased surface productivity. The onset of the terminal decline in Maastrichtian species richness began at 67.5 Ma and the first significant decline in surface productivity occurred at 66.2 Ma, coincident maximum cooling to 13°C in surface waters and the reduction of the surface-to-deep temperature gradient to less than 5°C. Major climatic and moderate productivity changes mark the mass extinction and the last 500 kyr of the Maastrichtian. Between 200 and 400 kyr before the K/T boundary surface and deep waters warmed rapidly by 3–4°C and cooled again during the last 100 kyr of the Maastrichtian. Surface productivity decreased only moderately across the K/T boundary. Species richness began to decline during the late Maastrichtian cooling and by K/T boundary time, the mass extinction had claimed 66% of the species. Viewed within the context of Maastrichtian climate and productivity changes, the K/T mass extinction could have resulted from extreme environmental stress even without the addition of an extraterrestrial impact.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/S0377839897000273
DOI10.1016/S0377-8398(97)00027-3
Short TitleMarine Micropaleontology

The Cretaceous-tertiary transition on the shallow Saharan Platform of southern tunisia

TitleThe Cretaceous-tertiary transition on the shallow Saharan Platform of southern tunisia
Publication TypeJournal Article
Year of Publication1998
AuthorsKeller, G, Adatte, T, Stinnesbeck, W, Stüben, D, Kramar, U, Berner, Z, Li, L, Perch-Nielsen, Kvon Salis
JournalGeobios
Volume30
Pagination951–975
Date Published01/1998
Abstract

A multidisciplinary approach to the study of a K/T boundary section on the Saharan Platform based on planktic and benthic foraminifera, calcareous nannofossils, lithology, stable isotopes, mineralogy and geochemistry reveals a biota stressed by fluctuating hyposaline, hypoxic littoral and nearshore environments, productivity changes, and a paleoclimate altering between seasonal warm to temperate and warm/humid conditions. Benthic formaminifera indicate that during the last 300 kyr of the Maastrichtian (CF1, Micula prinsii) deposition occurred in a inner neritic (littoral) environment that shallowed to a near-shore hyposaline and hypoxic environment during the last 100–200 kyr of the Maastrichtian. These conditions were accompanied by a seasonal warm to temperate climate that changed to warm/humid conditions with high rainfall, by decreasing surface productivity, and significantly decreasing planktic and benthic foraminiferal species richness. The K/T boundary is marked by an undulating erosional contact overlain by a 10 cm thick sandstone layer which is devoid of any exotic minerals or spherules. Their absence may be due to a short hiatus and the fact that the characteristic clay and red layer (zone P0) are missing. During the earliest Danian (Pla), low sea-levels prevailed with continued low oxygen, low salinity, high rainfall, high erosion and terrigenous sediment influx, accompanied by low diversity, low oxygen and low salinity tolerant species. These environmental conditions abruptly ended with erosion followed by deposition of a phosphatic siltstone layer that represents condensed sedimentation in an open (transgressive) marine environment. Above this layer, low sealevels and a return to near-shore, hyposaline and hypoxic conditions prevailed for a short interval [(base of Plc(2)] and are followed by the re-establishment of normal open marine conditions (inner neritic) comparable to the late Maastrichtian. This marine transgression is accompanied by increased productivity, and the first diversified Danian foraminiferal assemblages after the K/T boundary event and represents the return to normal biotic marine conditions. Though the K/T Seldja section represents one of the most shallow marginal sea environments studied to date for this interval, it does not represent isolated or atypical conditions. This is suggested by the similar global trends observed in sea-level fluctuations, hiatuses, as well as faunal assemblages. We conclude that on the Saharan platform of southern Tunisia, longterm environmental stresses beginning 100–200 kyr before the K/T boundary and related to climate, sea-level, nutrient, oxygen and salinity fluctuations, were the primary causes for the eventual demise of the Cretaceous fauna in the early Danian. The K/T boundary bolide impact appears to have had a relatively incidental short-term effect on this marine biota.  PDF

URLhttps://doi.org/10.1016/s0016-6995(97)80218-5
DOI10.1016/s0016-6995(97)80218-5

Analysis of El Kef blind test I

TitleAnalysis of El Kef blind test I
Publication TypeJournal Article
Year of Publication1997
AuthorsKeller, G
JournalMarine Micropaleontology
Volume29
Pagination89–93
Date Published01/1997
Abstract

The blind sample test was designed to determine whether the observed species extinction pattern across the K/T boundary supports Smit’s (1982, 1990) scenario of all but one species suddenly extinct at the K/T boundary, or Keller’s (1988b) scenario of gradual extinctions with some species disappearing below and the majority at the K/T boundary with l/3 ranging into the Danian. The blind test can only resolve the controversy regarding the observed pattern of extinction, and not the controversy regarding the interpretation of this pattern.

The Smit and Keller extinction models are shown in Figs. 11 and 12. Since Smit has not published a complete census list of Cretaceous taxa, his model is illustrated in Fig. 11 without species names. Keller’s (1988b) data are shown in Fig. 12 for six stratigraphic levels that are equivalent to the six blind test samples.

The four testers were asked to collect species census data from the >63 pm size fraction, provide relative abundances of each species and the benthic/ planktic ratio based on population counts of 300 to 400 individuals in a random sample split. Unfortunately, not all testers used the same data gathering methods and as a result the relative species abundances and benthic/planktic ratio data differ by more than one magnitude. These data are excluded from this analysis. The blind sample test therefore rests upon taxic census data only. Taxic census data, however, have their own problems. They essentially vary from tester to tester based on taxonomic concepts. This may result in different species names used for the same morphotypes among the four testers, or in several different species names given to morphotypes that some testers consider to be morphologic variants of the same species.

The degree to which different taxonomic concepts influenced the taxic census data is seen by the number of species identified and by the common species names used. In Maastrichtian samples, the number of species identified by each of the blind testers are: Canudo 47, Olsson 45, Masters 52, and Orueetxebarria 59; in similar samples, Keller (1988b) identified 51 species. All four testers used the same species names for 14 to 16 species and three testers used the same species names for 10 to 16 species. Taxonomic agreement for the remaining species is low. This illustrates the fact that taxic census data of the four testers cannot be compared on a species by species basis. Even if the same species names are used, there is no guarantee that all testers applied that species name to the same morphotype. But, we can be reasonably sure that each tester applied each species name to a distinct and different morphotype. For these reasons, comparison of the patterns of extinction of all taxa is more instructive than comparing extinction of species by species using the same species names.

There is no way taxonomic differences between testers can be identified and isolated in the data sets without getting them all together to sort out their taxonomic differences. But, doing so would defeat the purpose of the blind test which was to get a spectrum of outside views to compare and contrast with &nit’s (1982, 1990) and Keller’s (1988b) studies. The degree of variation between the testers is in itself an important and real variable of differences between workers and therefore must be preserved, if the test is to approximate the spectrum of opinions. The real test will be whether a common extinction pattern emerges from these analyses. If so, then individual variations in taxonomic concepts are less relevant. If no common extinction pattern emerges, then taxonomic differences override the actual data. In this section, patterns of extinction, irrespective of species names, are discussed first, followed by analysis of the statistical similarity between the stratigraphic position of species identified by each tester.   PDF

URLhttps://doi.org/10.1016/s0377-8398(96)00044-8
DOI10.1016/s0377-8398(96)00044-8

The Cretaceous/Tertiary boundary event in Ecuador: reduced biotic effects due to eastern boundary current setting

TitleThe Cretaceous/Tertiary boundary event in Ecuador: reduced biotic effects due to eastern boundary current setting
Publication TypeJournal Article
Year of Publication1997
AuthorsKeller, G, Adatte, T, Hollis, C, Ordóñez, M, Zambrano, I, Jiménez, N, Stinnesbeck, W, Aleman, A, Hale-Erlich, W
JournalMarine Micropaleontology
Volume31
Pagination97–133
Date Publishedaug
Abstract

A multidisciplinary study of a new Cretaceous-Tertiary (K/T) boundary section near Guayaquil, Ecuador, reveals an unusually cool water, low diversity planktic foraminiferal fauna and a high diversity radiolarian fauna similar to those found in southern high-latitude K/T sequences despite the fact that this section was deposited near the Cretaceous equator. The K/T boundary is located by planktic foraminifera within a narrow interval bounded by last appearances of tropical Cretaceous species and first appearances of Tertiary species including Parvularugoglobigerina eugubina. As in southern high latitudes, there is no major mass extinction of either planktic foraminifera or radiolarians at this level. A major radiolarian faunal discontinuity occurs some 6 m higher in the section within foraminiferal Zone Plc, some 300–500 kyr after the K/T event.

δ13C values from bulk carbonates show both high- and low-latitude characteristics. Similarly to low latitudes, there is a 3%. negative δ13C excursion at the K/T boundary which is generally interpreted as a major decrease in primary productivity. But unlike the low latitudes, recovery occurs within a few thousand years, as compared with 300–500 kyr, and suggests rapid nutrient influx from the Antarctic region via a current similar to the Humboldt current today. Similarly to high-latitude K/T sequences, a negative δ13C shift occurs in the early Danian Zone Plb about 300 kyr after the K/T boundary. Sedimentologic and mineralogic data indicate a late Maastrichtian with relatively low biogenic quartz and high carbonate followed by increasing biogenic quartz (>50%) and decreasing carbonate (<5%) during the early Danian. This suggests intensified atmospheric and oceanic circulation and upwelling off Ecuador during the early Danian. The K/T transition is marked by increased volcanic activity, continental erosion and terrigenous influx, but this also occurs in the early Danian Zone at the P1aP1b zonal transition and is thus not unique to the K/T boundary.

We suggest that the catastrophic biotic effects normally observed at the K/T boundary in low latitudes are greatly reduced or absent in the eastern equatorial Pacific because this region was dominated, then as now, by upwelling and current transport of nutrient-rich waters from the Antarctic Ocean. As a result, the biotic patterns are characteristic of southern high latitudes, whereas the δ13C pattern combines ameliorated low-latitude effects with predominantly high-latitude trends.   PDF

 

URLhttps://doi.org/10.1016/s0377-8398(96)00061-8
DOI10.1016/s0377-8398(96)00061-8

The Cretaceous–Tertiary transition in Guatemala: limestone breccia deposits from the South Petèn basin

TitleThe Cretaceous–Tertiary transition in Guatemala: limestone breccia deposits from the South Petèn basin
Publication TypeJournal Article
Year of Publication1997
AuthorsStinnesbeck, W, Keller, G, Cruz, Jd. l., León, Cd., MacLeod, N, Whittaker, JE
JournalGeol Rundsch
Volume86
Start Page686
Date Published05/1997
Abstract

Limestone breccia deposits in southern Mexico, Guatemala and Belize have recently been interpreted as proximal to distal ballistic fallout deposits, generated by a bolide impact that struck Yucatan at K/T boundary time. We review the age, lithology and the depositional environment of Þve K/T boundary sections in the South Pete«n area of Guatemala (Caribe, Aserradero, Chisec, Actela, Chemal) in order to evaluate the nature and origin of K/T limestone breccia deposition. The sections are located 500 km south of the proposed impact site at Chicxulub and trend in an eastÐwest direction from the Guatemala/Mexico border to southern Belize. In four of the Þve sections examined, a breccia unit up to 50 m thick overlies reef-bearing shallow-water limestones of late Cretaceous (Campanian-Maastrichtian) age. Rhythmically bedded limestones, marls and siltstones of early Danian age overlie the breccia and were deposited under middle-to outer-neritic conditions. The breccia consists of di¤erently coloured layers of shallow-water limestones. Clast size generally decreases upsection to thin layers of predominantly rounded clasts, and these Þnegrained rudstones grade into grainstones at the top. In at least one section (EI Caribe) diagenetically altered glass spherules are present in the uppermost layers of the grainstone. These glass spherules are of strati- W. Stinnesbeck ( ) Geologisches Institut der Universita¬ t Karlsruhe, Postfach 6980, D-76128 Karlsruhe, Germany Fax:#0721 608 2138 G. Keller Department of Geosciences, Princeton University, Princeton, NJ 08544, USA J. de la Cruz á Carlos de Leo«n Ministerio de Energõ«a y Minas, Direccio«n de Hidrocarburos, Diagonal 17, 29Ð78, Zona 11, Guatemala 01011, Guatemala N. MacLeod á J. E. Whittaker Department of Paleontology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK graphic position and chemical composition similar to black and yellow glass from Beloc, Haiti and Mimbral, Mexico, which some workers have chemically linked to melt glass within the breccia of the Chicxulub cores. We suggest that breccia deposition in Guatemala may have been multi-event, over an extended time period, and related to the collision of the Yucatan and Chortis plates as well as related to a major impact or volcanic event at the end of the Cretaceous.  PDF

URLhttp://link.springer.com/article/10.1007%2Fs005310050171

Near-K/T age of clastic deposits from Texas to Brazil: impact, volcanism and/or sea-level lowstand?

TitleNear-K/T age of clastic deposits from Texas to Brazil: impact, volcanism and/or sea-level lowstand?
Publication TypeJournal Article
Year of Publication1996
AuthorsKeller, G, Stinnesbeck, W
JournalTerra Nova
Volume8
Pagination277–285
Date Publishedmay
Abstract

Near-K/T boundary clastic deposits from Texas, Mexico, Haiti, Guatemala and Brazil, often described as impact-generated tsunami deposits, are stratigraphically below well-defined K/T boundary horizons and appear not to be causally related to the K/T boundary event. Stratigraphic evidence indicates that their deposition began during the last 170–200 kyr of the Maastrichtian, coincident with a major eustatic sea-level lowstand that lowered sea level by as much as 70–100 m. Clastic deposition ended a few tens of thousands of years before the K/T boundary during a rapidly rising sea level. The presence of glass in clastic deposits in Haiti, northeastern Mexico and Yucatan suggests that the sea-level lowstand coincided with a time of major volcanism or pre-K/T boundary bolide impact.  PDF

URLhttps://doi.org/10.1111/j.1365-3121.1996.tb00757.x
DOI10.1111/j.1365-3121.1996.tb00757.x

K/T boundary coarse-grained siliciclastic deposits in northeastern Mexico and northeastern Brazil: Evidence for mega-tsunami or sea-level changes?

TitleK/T boundary coarse-grained siliciclastic deposits in northeastern Mexico and northeastern Brazil: Evidence for mega-tsunami or sea-level changes?
Publication TypeBook Chapter
Year of Publication1996
AuthorsStinnesbeck, W, Keller, G
Book TitleSpecial Paper 307: The Cretaceous-Tertiary Event and Other Catastrophes in Earth History
Pagination197–209
PublisherGeological Society of America
Abstract

Coarse-grained siliciclastic and limestone breccia deposits have been described from over a dozen K/T boundary sections in northeastern Mexico and variously interpreted as the result of an impact-generated mega-tsunami or sea-level low stand. In addition, a K/T boundary sequence in northeastern Brazil has been reinterpreted as the result of two bolide impacts. In both regions, the clastic deposits are presumed to have originated as a result of a bolide impact on Yucatan. We review the age, biostratigraphy, lithology, and depositional environment of these deposits in order to evaluate the time of deposition and their stratigraphic relationship to the K/T boundary event. Our observations indicate that the near–K/T boundary siliciclastic deposits of northeastern Mexico cannot be explained by deposition resulting from a single catastrophic event. They appear to have been deposited by normal sedimentary processes over an extended time period spanning thousands of years. This is indicated by the presence of multiple bioturbation horizons, discrete layers of normal hemipelagic sedimentation within the clastic deposits, and mineralogically and sedimentologically discrete horizons correlatable over 300 km. Such correlations do not support chaotic single-event deposition. Clastic deposition occurred sometime during the last l70 to 200 k.y. of the Maastrichtian but ended sometime before the K/T boundary. This is indicated by the presence of the index species Plummerita hantkeninoides. These deposits stratigraphically correlate with the limeclast breccia of the Poty section in northeastern Brazil, which also predates the K/T boundary. Benthic foraminifers indicate that deposition of the limestone breccia at Poty and siliciclastic sediments in northeastern Mexico coincided with a eustatic sea-level low stand that lowered sea level by 70 to l00 m. The coincidence of clastic deposition with the latest Maastrichtian sea-level low stand suggests that they are causally related. However, since clastic deposition is not necessarily related to sea-level regressions, and the glass-bearing deposits in northeastern Mexico are unique, a pre–K/T boundary event (bolide impact or volcanism) cannot be excluded.   PDF

URLhttps://doi.org/10.1130/0-8137-2307-8.197
DOI10.1130/0-8137-2307-8.197

Cretaceous-Tertiary (K/T) mass extinction: effect of global change on calcareous microplankton

TitleCretaceous-Tertiary (K/T) mass extinction: effect of global change on calcareous microplankton
Publication TypeBook Chapter
Year of Publication1995
AuthorsKeller, G, Perch-Nielsen, K
Book TitleEffects of Past Global Change on Life, S. Stanley and J.P. Kennett (eds.)
Pagination72-93
PublisherNational Academy of Science
Abstract

The effects of the Cretaceous-Tertiary (K/T) boundary global change on calcareous nannoplankton and planktic foraminifera are most severe in low latitudes and negligible in high latitudes. In low latitudes, species extinctions are complex and prolonged beginning during the final 100,000 to 300,000 yr of the Cretaceous, accelerating across the K/T boundary, and reaching maximum negative conditions between 10,000 and 40,000 yr into the Tertiary accompanied by low primary productivity. In high latitudes, no significant species extinctions occurred at or near the K/T boundary, and all dominant species thrived well into the early Tertiary. Return to a more stable ecosystem and to increased marine productivity in low latitudes does not occur until about 250,000 to 350,000 yr after the K/T boundary, coincident with the extinction of Cretaceous survivors in high latitudes. Within this transition interval, habitats of deep- and intermediate-dwelling tropical planktic foraminiferal species are gradually and selectively eliminated in low latitudes, and by K/T boundary time only cosmopolitan surface dwellers survive. This implies the disruption of the water-mass structure, change in the thermocline, and a drop in surface productivity. Although no single cause is likely to account for these different prolonged and dramatic faunal and environmental changes between low and high latitudes, long-term oceanic instability associated with sea-level, temperature, salinity, and productivity fluctuations may account for most of the faunal changes observed in planktic foraminifera. However, other environmental changes (e.g., volcanism, bolide impact) may have accelerated the demise of the low latitude Cretaceous fauna already on the decline.

URLhttps://www.nap.edu/read/4762/chapter/6

The Cretaceous/Tertiary boundary stratotype section at El Kef, Tunisia: how catastrophic was the mass extinction?

TitleThe Cretaceous/Tertiary boundary stratotype section at El Kef, Tunisia: how catastrophic was the mass extinction?
Publication TypeJournal Article
Year of Publication1995
AuthorsKeller, G, Li, L, MacLeod, N
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume119
Issue3-4
Pagination221 - 254
Date PublishedJan-01-1996
ISSN00310182
Abstract

The Cretaceous/Tertiary (K/T) boundary stratotype section at El Kef, Tunisia, represents the most complete and expanded sedimentary record across this important mass extinction horizon presently known. High resolution analysis of planktic foraminifera in two outcrops (El Kef I—stratotype and El Kef II) along with comparisons between planktic and benthic foraminifera, calcareous nannofossils, ostracods, pollen and spores, and dinoflagellates indicate that major changes across the K/T boundary are registered only in benthic and planktic foraminifera and calcareous nannofossils. Biotic changes in benthic foraminifera are unique to El Kef and similarly shallow continental shelf sections and appear to be the result of a sea-level regression in the latest Maastrichtian followed by a sea-level rise across the K/T boundary that was accompanied by expansion of the local oxygen minimum zone (OMZ). Biotic changes in planktic foraminifera appear partly related to these conditions also, but in general reflect more global oceanographic changes. For instance, species extinctions are gradual and selective as observed in K/T sections worldwide, rather than random and abrupt. Although there is a 69% decline in species richness between 25 cm below and 10 cm above the K/T boundary, only rare species disappeared. Their combined relative abundance constitute less than 20% of the total population. About 52% of these extinct taxa (8% of the population) are large, ornate, morphologically complex tropical-subtropical forms that lived at or below the thermocline. No planktic foraminifera from this depth range survived the K/T boundary event. All survivor taxa were surface dwellers living within the photic zone. Their relative abundance (∼80%) dominates both Cretaceous and early Tertiary populations.

These data indicate that the K/T biotic record in the shallow continental shelf section at El Kef was significantly influenced by local conditions which, combined with the latest Maastrichtian sea-level regression and subsequent sea-level rise, resulted in shallowing of the local OMZ relative to the sea-surface. Shallowing of the local OMZ lead to the selective disappearance of benthic faunas and may have adversely affected the surviving photic zone dwellers. The selective nature of species extinctions, however, appear to be related partly to long-term global oceanographic changes which were accelerated at the K/T boundary possibly by a bolide impact. PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/0031018295000097
DOI10.1016/0031-0182(95)00009-7
Short TitlePalaeogeography, Palaeoclimatology, Palaeoecology

Field Guide to the Cretaceous-Tertiary boundary section at Poty, north of Recife, northeastern Brazil

TitleField Guide to the Cretaceous-Tertiary boundary section at Poty, north of Recife, northeastern Brazil
Publication TypeBook Chapter
Year of Publication1994
AuthorsStinnesbeck, W, Keller, G
Pagination1-19
Publisher14th International Sedimentological Congress (IAS 94)
CityRecife
Abstract

Only one K/T complete section (Poty Quarry, Recife, Brazil,Fig. 1) has been reported to date from the South American continent (Stinnesbeck, 1989; Alberta0 et al., 1994; Stinnesbeck and Keller, 1994, 1996). The Poty Quarry is similar to northeastern Mexico sections in that both contain typical Tethys planktic foraminiferal assemblages and an 'event' deposit (siliciclastic and breccia deposits) stratigraphically below the K/T boundary (Keller and Stinnesbeck, 1996b)

Comparative biogeographic analysis of planktic foraminiferal survivorship across the Cretaceous/Tertiary (K/T) boundary

TitleComparative biogeographic analysis of planktic foraminiferal survivorship across the Cretaceous/Tertiary (K/T) boundary
Publication TypeJournal Article
Year of Publication1994
AuthorsMacLeod, N, Keller, G
JournalPaleobiology
Volume20
Pagination143–177
Abstract

It is now widely recognized that a large number of Cretaceous planktic foraminiferal species are commonly found associated with fully Danian faunas in many K/T boundary sections and deep-sea cores. This “Cretaceous” fauna has traditionally been regarded as representing the reworking of older Cretaceous sediments into younger strata, though recent isotopic data from some species indicates that, at least in these instances, the reworking hypothesis is false. To further test this reworking hypothesis the biogeography of this “Cretaceous” fauna is compared to the underlying uppermost Maastrichtian biogeography and to the biogeography of lowermost Danian planktic foraminiferal faunas. Results show that there is no regular decline in species richness, extinction, or faunal co-occurrence values for this “Cretaceous” fauna at progressively higher (=younger) Danian stratigraphic horizons. Moreover, there is no compelling association between the stratigraphic persistence of this “Cretaceous” fauna and shallow depositional settings. Instead, this fauna is characterized by: (1) a close (and predictive) association between “Cretaceous” and indigenous Danian species richness values throughout the lower Danian, (2) a close numerical and geographic correspondence between Danian speciation and the disappearance of “Cretaceous” species from the Danian fossil record, and (3) a pronounced similarity between changes in the general biogeographic structures of the “Cretaceous” and associated Danian faunas throughout the study interval. These data suggest that the K/T planktic foraminiferal extinction event exhibited a marked geographic structure with low and middle latitude faunas experiencing differentially high extinction rates in the lowermost Danian zones P0 and P1a and high latitude survivor faunas persisting more or less unchanged into the overlying zone, P1b and P1c. Taken together, these results challenge the traditional concept of an instantaneous uppermost Cretaceous planktic foraminiferal mass extinction and its proposed causal connection to bolide impact.

URLhttps://doi.org/10.1017/s0094837300012653
DOI10.1017/s0094837300012653

Age, Deposition and Biotic Effects of the Cretaceous/Tertiary Boundary Event at Mimbral, NE Mexico

TitleAge, Deposition and Biotic Effects of the Cretaceous/Tertiary Boundary Event at Mimbral, NE Mexico
Publication TypeJournal Article
Year of Publication1994
AuthorsKeller, G, Stinnesbeck, W, Lopez-Oliva, JGuadelupe
JournalPALAIOS
Volume9
Pagination144-157
ISSN08831351, 19385323
Abstract

The Mimbral outcrop in northeastern Mexico represents nearly continuous sedimentation across the Cretaceous/Tertiary (K/T) transition. The K/T boundary is present in a 4 cm clay layer and 3 mm red layer above the top of a channel-fill deposit. The 60 m wide and 3 m high channel-fill deposit is of latest Maastrichtian age (A. mayaroensis Zone). It consists off aunally, lithologically and mineralogically distinct units that appear to represent a series of gravity flows related to the latest Maastrichtian sea-level lowstand. The biotic effects of the K/T boundary event were not catastrophic for planktic foraminiferal faunas at Mimbral, NE Mexico. Although 2/3 of the species disappeared at or below the K/T boundary, the effect on the overall foraminiferal population was small (<17%) because only rare, already endangered taxa disappeared. These taxa were specialized tropical and subtropical forms intolerant of environmental changes. The dominant taxa (>83%) consist of cosmopolitan forms tolerant of wide ranging environmental conditions. These survived the K/T boundary event without any sudden changes in their relative abundance. Their terminal decline about 100,000 years after the K/T boundary appears to be related to competition from the evolving Tertiary fauna. The limited biotic effects observed across the K/T boundary at Mimbral are consistent with other low latitude sections, and indicate that if a bolide impact occurred in the Caribbean, the biologic consequences were not as catastrophic as generally assumed even within a radius of 2000 miles.  PDF

URLhttp://www.jstor.org/stable/3515102

Reply to comment on `The Cretaceous-Tertiary boundary transition in the Antarctic Ocean and its global implications'

TitleReply to comment on `The Cretaceous-Tertiary boundary transition in the Antarctic Ocean and its global implications'
Publication TypeJournal Article
Year of Publication1994
AuthorsKeller, G, MacLeod, N
JournalMarine Micropaleontology
Volume24
Pagination101–118
Date Published12/1994
Abstract

The critique of Huber et al. ( 1994-this volume) follows two lines of argument. The first is that Keller (1993) does not confirm Huber's ( 1991 ) earlier study. The second is devoted to criticizing Keller (1993) for not following the revised taxonomy of Olsson et al. (1992), Liu and Olsson (1992) and Olsson and Liu (1993). Huber et al. ( 1994-this volume) do not mention the fact that none of these studies were published at the time the paper they criticize was written (during the fall of 1991). But even if these studies had been known, they would not have influenced the arguments presented by Keller (1993) since none of these publications provides convincing arguments in favor of their proposed taxonomic revisions (for a critique see MacLeod, 1993, in press a,b). In addition, Huber et al. ( 1994-this volume) criticize Keller for not following the Berggren and Miller (1988) Paleogene biozonation.   PDF

URLhttps://doi.org/10.1016/0377-8398(94)90018-3
DOI10.1016/0377-8398(94)90018-3

Productivity across the Cretaceous/Tertiary boundary in high latitudes

TitleProductivity across the Cretaceous/Tertiary boundary in high latitudes
Publication TypeJournal Article
Year of Publication1994
AuthorsBarrera, E, Keller, G
JournalGeological Society of America Bulletin
Volume106
Pagination1254–1266
Date Publishedoct
Abstract

In low and middle latitudes, the Cretaceous/Tertiary boundary is marked by a sudden and pronounced decrease in δ13C values of near-surface-water carbonates and a reduction in the surface-to-bottom δ13C gradient. These isotopic data have been interpreted as evidence of a decline in surface-water productivity that was responsible for the extinction of many planktic foraminiferal species and other marine organisms at or near the K/T boundary. We present planktic and benthic foraminiferal isotopic data from two almost biostratigraphically complete sections at Ocean Drilling Program Site 738 in the antarctic Indian Ocean and at Nye Kløv in Denmark. These data suggest that planktic carbonate δ13C values in high latitudes may not have decreased dramatically at the K/T boundary; thus, surface-water productivity may not have been reduced as much as in low and middle latitudes. Comparison of the records of Site 738 with those of ODP Sites 690 and 750 indicates a pronounced decline in δ13C values of planktic and benthic foraminifera and fine-fraction/bulk carbonate ∼200 000 yr after the K/T boundary. This reflects a regional shift in the carbon isotopic composition of oceanic total dissolved carbon (TDC) and correlates with a similar change in benthic foraminiferal δ13C values at mid- and low-latitude Deep Sea Drilling Project Sites 527 and 577. This oceanographic event was followed by the ecosystem's global recovery ∼500 000 yr after the K/T boundary. These data suggest that the environmental effects of the K/T boundary may have been less severe in the high-latitude oceans than in tropical and subtropical regions.   PDF

URLhttps://doi.org/10.1130/0016-7606(1994)106<1254:patctb>2.3.co;2
DOI10.1130/0016-7606(1994)106<1254:patctb>2.3.co;2

The Cretaceous-Tertiary boundary transition in the Antarctic Ocean and its global implications

TitleThe Cretaceous-Tertiary boundary transition in the Antarctic Ocean and its global implications
Publication TypeJournal Article
Year of Publication1993
AuthorsKeller, G
JournalMarine Micropaleontology
Volume21
Issue1-3
Pagination1 - 45
Date PublishedJan-04-1993
ISSN03778398
Abstract

Three Antarctic Ocean K/T boundary sequences from ODP Site 738C on the Kerguelen Plateau, ODP Site, 752B on Broken Ridge and ODP Site 690C on Maud Rise, Weddell Sea, have been analyzed for stratigraphic completeness and faunal turnover based on quantitative planktic foraminiferal studies. Results show that Site 738C, which has a laminated clay layer spanning the K/T boundary, is biostratigraphically complete with the earliest Tertiary Zones P0 and P1a present, but with short intrazonal hiatuses. Site 752B may be biostratigraphically complete and Site 690C has a hiatus at the K/T boundary with Zones P0 and P1a missing.

Latest Cretaceous to earliest Tertiary planktic foraminiferal faunas from the Antarctic Ocean are cosmopolitan and similar to coeval faunas dominating in low, middle and northern high latitudes, although a few endemic species are present. This allows application of the current low and middle latitude zonation to Antarctic K/T boundary sequences. The most abundant endemic species is Chiloguembelina waiparaensis, which was believed to have evolved in the early Tertiary, but which apparently evolved as early as Chron 30N at Site 738C. Since this species is only rare in sediments of Site 690C in the Weddell Sea, this suggests that a watermass oceanographic barrier may have existed between the Indian and Atlantic Antarctic Oceans.

The cosmopolitan nature of the dominant fauna began during the last 200,000 to 300,000 years of the Cretaceous and continued at least 300,000 years into the Tertiary. This indicates a long-term environmental crisis that led to gradual elimination of specialized forms and takeover by generalists tolerant of wide ranging temperature, oxygen, salinity and nutrient conditions. A few thousand years before the K/T boundary these generalists gradually declined in abundance and species became generally dwarfed due to increased environmental stress. There is no evidence of a sudden mass killing of the Cretaceous fauna associated with a bolide impact at the K/T boundary. Instead, the already declining Cretaceous taxa gradually disappear in the early Danian and the opportunistic survivor taxa (Ch. waiparaensis andGuembelitria cretacea) increase in relative abundance coincident with the evolution of the first new Tertiary species.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/037783989390010U
DOI10.1016/0377-8398(93)90010-U
Short TitleMarine Micropaleontology

Gradual mass extinction, species survivorship, and long-term environmental changes across the Cretaceous-Tertiary boundary in high latitudes

TitleGradual mass extinction, species survivorship, and long-term environmental changes across the Cretaceous-Tertiary boundary in high latitudes
Publication TypeJournal Article
Year of Publication1993
AuthorsKeller, G, BARRERA, E, SCHMITZ, B, MATTSON, E
JournalGeological Society of America Bulletin
Volume105
Issue8
Pagination979 - 997
Date PublishedJan-08-1993
ISSN00167606
Abstract

Stable-isotope and planktic foraminiferal analyses across the Cretaceous/Tertiary (K/T) boundary transition at Nye Klov indicate longterm oceanic instability associated with global sea-level fluctuations, a gradual mass extinction, and decreased magnitude of the δ13C shift in high latitudes.

Oceanic instability, which began at least 100 kyr before the K/T boundary and continued for about 300 kyr into the Tertiary, was accompanied by a gradual faunal turnover. The maximum sea-level lowstand during latest Maastrichtian is recorded about 75 cm below the K/T boundary. A sea-level rise first in evidence at 20 cm to 40 cm below the boundary continued into Zone P0 (boundaiy clay). This sea-level rise was accompanied by 2 °C of cooling in surface and bottom waters prior to the K/T boundary. δ13C values remained relatively stable up to 10 cm below the K/T boundary. A negative shift of 0.5 to 1.0 per mil occurred in the boundary clay in both planktic and benthic foraminifera. The surface to deep δ13C gradient remained nearly unchanged, in contrast to low latitudes, where this gradient is virtually eliminated. No sudden mass extinction occurred in this cosmopolitan, high-latitude fauna, and nearly all Cretaceous taxa thrived well into the Tertiary, when they gradually disappeared. Shallow seas, dominated by Cretaceous survivor taxa and a well-developed oxygen minimum zone, prevailed during the earliest Tertiary. Short-term sea-level lowstands are marked by hiatuses at the top of Zones P0 and Pla about 50 kyr and 230 kyr after the K/T boundary, respectively. Rising sea level reestablished normal marine conditions about 300 kyr to 350 kyr after the K/T boundary, coincident with the first post-K/T boundary recovery of the Tertiary fauna and extinction of Cretaceous survivors. During this Geological Society of America Bulletin, v. 105, p. time, high-latitude regions temporarily acted as centers of origin and dispersal for planktic foraminifera.

Long-term oceanic instability, gradual faunal turnover, absence of a sudden mass extinction, and greatly diminished δ13C shift in high latitudes suggest that a K/T boundary bolide impact was not the primary cause for the K/T boundary faunal transition. Moreover, these data strongly imply that the destructive effects of the bolide impact would have been greatest in low latitudes and negligible in high latitudes regions temporarily acted as centers of origin and dispersal for planktic foraminifera.

Long-term oceanic instability, gradual faunal turnover, absence of a sudden mass extinction, and greatly diminished δ13C shift in high latitudes suggest that a K/T boundary bolide impact was not a primary cause for the K/T boundary faunal transition. Moreover, these data strongly imply that the destructive effects of the bolide impact would have been greatest in low latitudes and negligible in high latitudes.  PDF

URLhttp://gsabulletin.gsapubs.org/cgi/doi/10.1130/0016-7606(1993)105<0979:GMESSA>2.3.CO;2http://bulletin.geoscienceworld.org/cgi/doi/10.1130/0016-7606(1993)105%3C0979:GMESSA%3E2.3.CO;2
DOI10.1130/0016-7606(1993)105<0979:GMESSA>2.3.CO;2

Carbon isotopic evidence for biomass burning at the K-T boundary: Comment and Reply

TitleCarbon isotopic evidence for biomass burning at the K-T boundary: Comment and Reply
Publication TypeJournal Article
Year of Publication1993
AuthorsKeller, G, MacLeod, N, Ivany, LC, Salawitch, RJ
JournalGeology
Volume21
Pagination1149
Abstract

A new interpretation of existing carbon isotopic data combined with results from a biogeochemical model suggests that burning of terrestrial biomass occurred on a global scale at the Cretaceous-Tertiary (K-T) boundary. Carbon isotopic ratios from planktonic and benthic microfossils across the K-T boundary reveal not only a breakdown in the normal surface-water to deep-water gradient of 13C/12C, but also a reversal at the boundary. This reversal cannot be explained by the cessation off primary production alone. We propose that combustion of terrestrial biomass with subsequent transfer of isotopically light carbon to surface waters is the most likely cause of this anomaly. A biogeochemical model is used to quantify the extent of burning at the boundary. combustion of roughly 25% of the above-ground biomass at the end of the Cretaceous is necessary to account for the observed isotopic signal.  PDF

URLhttps://doi.org/10.1130/0091-7613(1993)021<1149:ciefbb>2.3.co;2
DOI10.1130/0091-7613(1993)021<1149:ciefbb>2.3.co;2

Early diageneitc isotopic signal at the Cretaceous/Tertiary boundary, Israel

TitleEarly diageneitc isotopic signal at the Cretaceous/Tertiary boundary, Israel
Publication TypeJournal Article
Year of Publication1992
AuthorsMagaritz, M, Benjamini, C, Keller, G, Moshkovitz, S
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume91
Pagination291–304
Date Publishedfeb
Abstract

Carbon and oxygen isotope records from carbonate fractions in marls overlying the K/T boundary in southern Israel are used to interpret paleoenvironmental changes and the history of early diagenetic events in the earliest Tertiary. The δ13C record of the whole rock does not significantly depart from the original values and reflects the global productivity drop shortly after the K/T boundary and the subsequent recovery. Fine fraction oxygen isotope values reflect the addition of carbonate cement highly depleted in 18O throughout the profile. The δ18O record demonstrates two main episodes in which contact with fresh water affected the sediments. One is below a short hiatus at planktic foraminiferal subzone transition PO/P1a (Guembelitria cretacea/Parvularugoglobigerina eugubina) and the other at an pyrite- rich clay layer near the top to planktic foraminiferal subzone P1b (‘Globigerina’ taurica). The latter event suggests introduction of sapropelic bottom conditions in the oceanic paleoenvironment.   PDF

 

URLhttps://doi.org/10.1016/0031-0182(92)90073-e
DOI10.1016/0031-0182(92)90073-e

Stable isotope and foraminiferal changes across the Cretaceous—Tertiary boundary at Stevns Klint, Denmark: Arguments for long-term oceanic instability before and after bolide-impact event

TitleStable isotope and foraminiferal changes across the Cretaceous—Tertiary boundary at Stevns Klint, Denmark: Arguments for long-term oceanic instability before and after bolide-impact event
Publication TypeJournal Article
Year of Publication1992
AuthorsSchmitz, B, Keller, G, Stenvall, O
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume96
Pagination233–260
Date Published10/1992
Abstract

Stable isotope and planktic and benthic foraminiferal analyses of the K/T boundary transition at Stevens Klint, Denmark, indicate a 100–500 kyr long period of instability in oceanic bottom-water temperature and sea level. During the latest Maastrichtian (from 2.7 m below and up to the K/T boundary) bottom-water temperatures gradually cooled about 1.5°C as surface water temperatures remained constant. At the K/T boundary bottom water temperatures decreased additionally 3°C, and then returned to pre-boundary values just above the boundary interval. Coincident with the onset of the first temperature decrease there was a prominent sea-level fall, estimated between 50–100 m as observed in benthic and planktic foraminiferal assemblages as well as in a decreasing surface-to-bottom δ13C gradient. About 40 cm below the iridium-rich K/T boundary clay, sea level began to rise. Poor preservation of foraminifera above the K/T boundary allows only tentative interpretation of Danian events at Stevns Klint, however, sea level generally continued to rise interrupted by short sea level falls. Associated with the observed sea-level changes are three important hiatuses: At the contact between the white chalk and overlying grey-white bryozoan chalk about 2.7 m below the K/T boundary, at or near the top of the Fish Clay (Zone Pla, Parvularugoglobigerina eugubina missing) and at the contact of the Cerithium Limestone and overlying Bryozoan Limestone about 60 cm above the K/T boundary (part of Zone Plc missing). These unconformities are coeval with hiatuses observed in many continental shelf sections and indicate a global eustatic rather than regional isostatic response. Notable is that at Stevns Klint the episode of oceanic instability is registered over approximately the same stratigraphic interval in which supposed extraterrestrial amino acids occur, a circumstance that may indicate a connection.

A gradual positive shift in δ13C is registered in both benthic and planktic foraminiferal assemblages in the upper Maastrichtian at Stevns Klint. The positive shift is followed by a prominent negative δ13C shift (1.3%) at the K/T boundary. An upper Maastrichtian positive δ13C excursion followed by a negativeδ13C anomaly at or near the K/T boundary has previously been observed in deep-sea cores from the Pacific Ocean and the Weddell Sea, Antarctica, implying a global event. Previous suggestions of a relation between the uppermost Maastrichtian positive δ13C excursion and sea-level variation are not supported by the data for Stevns Klint.  PDF

URLhttps://doi.org/10.1016/0031-0182(92)90104-d
DOI10.1016/0031-0182(92)90104-d

Extended period of extinctions across the Cretaceous/Tertiary boundary in planktonic foraminifera of continental-shelf sections: Implications for impact and volcanism theories: Discussion and reply

TitleExtended period of extinctions across the Cretaceous/Tertiary boundary in planktonic foraminifera of continental-shelf sections: Implications for impact and volcanism theories: Discussion and reply
Publication TypeJournal Article
Year of Publication1991
AuthorsBourgeois, J, Keller, G
JournalGeological Society of America Bulletin
Volume103
Pagination434–436
Date Publishedmar
Abstract

Extended period of extinctions across the Cretaceous/Tertiary boundary in planktonic foraminifera of continental-shelf sections: Implications for impact and volcanism theories: Discussion and reply.  PDF

URLhttps://doi.org/10.1130/0016-7606(1991)103<0434:epoeat>2.3.co;2
DOI10.1130/0016-7606(1991)103<0434:epoeat>2.3.co;2

How complete are Cretaceous/Tertiary boundary sections? A chronostratigraphic estimate based on graphic correlation

TitleHow complete are Cretaceous/Tertiary boundary sections? A chronostratigraphic estimate based on graphic correlation
Publication TypeJournal Article
Year of Publication1991
AuthorsMacLeod, N, Keller, G
JournalGeological Society of America Bulletin
Volume103
Pagination1439
Abstract

Cogent interpretations of data bearing on the Cretaceous/Tertiary (K/T) extinction controversy depend on the existence of accurate chronostratigraphic models for the various K/T boundary sections. We have employed the graphic correlation technique to summarize biostratigraphic and lithostratigraphic data from 15 intensively sampled K/T boundary sections within a common chronostratigraphic model. Our results indicate that almost all of these sections, along with 13 additional boundary sections not used to construct the model, contain prolonged and in many cases multiple hiatuses. Of these 28 boundary sections, only six were found to contain a continuous record of sediment accumulation across the K/T boundary itself. These six K/T-complete sections are El Kef (Tunisia), Agost (Spain), Caravaca (Spain), and three sections along the Brazos River (Texas).

A comparative analysis of hiatus distributions among these 28 K/T boundary sections also reveals the presence of systematic differences between continental-shelf and deep-sea depositional environments. The lower Danian interval immediately following the K/T boundary, and extending into biochronozones P0 and P1a, is typically missing from the deep sea, whereas boundary sections deposited in shallower middle-neritic to upper-slope environments are in most cases complete across the K/T boundary. These shallow, neritic boundary sections, however, are in many instances disrupted by hiatuses at the P0/P1a boundary and again in the upper part of Zone P1a. These differential patterns of hiatus distribution between deep-sea and continental-shelf depositional settings appear to be linked to sea-level fluctuations. Our data suggest that the apparently sudden mass extinction of planktonic Foraminifera and anomalies in the occurrence of geochemical tracers that are characteristic of the K/T boundary in deep-sea sections may be artifacts of a temporally incomplete deep-sea stratigraphic record.  PDF

URLhttps://doi.org/10.1130/0016-7606(1991)103<1439:hcactb>2.3.co;2
DOI10.1130/0016-7606(1991)103<1439:hcactb>2.3.co;2

Cretaceous/Tertiary boundary extinction pattern and faunal turnover at Agost and Caravaca, S.E. Spain

TitleCretaceous/Tertiary boundary extinction pattern and faunal turnover at Agost and Caravaca, S.E. Spain
Publication TypeJournal Article
Year of Publication1991
AuthorsCanudo, JI, Keller, G, Molina, E
JournalMarine Micropaleontology
Volume17
Pagination319–341
Date Published07/1991
Abstract

Planktonic foraminiferal extinctions at Caravaca and Agost occurred over an extended time period similar to El Kef and Brazos River. Some species disappeared well below the boundary. About 39–45% of the species, but less than 15% of the individuals in the population, became extinct at or near the K/T boundary. A second phase of extinction occurred at the top of the boundary clay (PO/Pla) and the remaining Cretaceous species (exceptG. cretacea) disappeared in Subzone Pla. Species extinctions were selective eliminating geographically restricted large, complex and deeper dwelling forms first and favoring survival of cosmopolitan small, simple surface dwellers. Only surface dwellers survived the K/T boundary event, whereas all deeper dwelling species, as well as some surface dwellers, disappeared at the boundary.

We interprete the selective abundance decline during the latest Cretaceous as a result of the seal level regression that reached a maximum just prior to the K/T boundary. The highly selective nature of the two-phased species extinctions at and above the boundary, we believe to be related to the major reduction in surface productivity and the breakdown in the water mass stratification that was associated with the rapid sea level transgression across the K/T boundary. A bolide impact however, may have hastened the demise of an already declining Cretaceous fauna.   PDF

URLhttps://doi.org/10.1016/0377-8398(91)90019-3
DOI10.1016/0377-8398(91)90019-3

Some patterns of planktic foraminiferal assemblage turnover at the Cretaceous-Tertiary boundary

TitleSome patterns of planktic foraminiferal assemblage turnover at the Cretaceous-Tertiary boundary
Publication TypeJournal Article
Year of Publication1991
AuthorsD'Hondt, S, Keller, G
JournalMarine Micropaleontology
Volume17
Pagination77–118
Date Published03/1991
Abstract

Three uppermost Cretaceous through basal Paleocene stratigraphic sequences are examined for planktic foraminiferal assemblage stability and temporal succession patterns. These sequences are at mid-latitude South Atlantic DSDP Site 528, then-equatorial Pacific DSDP Site 577 and the Tethyan shelf Ben Gurion section of the Negev, Israel. In order to better estimate biogeographic patterns and habitat preferences, the results of these analyses are compared to previous Cretaceous biogeographic studies and to previous analyses of Cretaceous-Tertiary (K/T) boundary shelf and epicontinental sections.

Results indicate that immediately following the K/T boundary, the examined epicontinental and open-ocean sites were exploited primarily by previously epicontinental planktic foraminiferal assemblages. This pattern of K/T boundary assemblage dominance suggests the geologically instantaneous break-down of Late Cretaceous epicontinental and open-ocean biogeographic provincialization. This shift in open-ocean foraminiferal assemblages is not consistent with models of non-selective K/T boundary extinctions, but is consistent with models of extinction resistence and offshore expansion of near-shore taxa.

The re-establishment of stable biogeographic differences between open-ocean and epicontinental planktic foraminiferal assemblages occurs by the basalParvularugoglobigerina eugubina Zone. At open-ocean sites 528 and 577 and the outer-shelf Ben Gurion section, PO andP. eugubina Zone faunal records are marked by a pronounced alternation between Paleocene biserial- and non-biserial-dominated assemblages. This alternation appears strongly damped at shelf and epicontinental sections previously examined. The first appearance and peak magnitude of abundant earliest Paleocene trochospiral forms (Parvularugoglobigerina, Eoglobigerina, Morozovella, Globoconusa) also vary from site to site and may depend closely on levels of primary carbonate productivity.  PDF

URLhttps://doi.org/10.1016/0377-8398(91)90024-z
DOI10.1016/0377-8398(91)90024-z

Faunal, erosional, and CaCO3 events in the early Tertiary eastern Tethys

TitleFaunal, erosional, and CaCO3 events in the early Tertiary eastern Tethys
Publication TypeBook Chapter
Year of Publication1990
AuthorsKeller, G, Benjamini, C, Magaritz, M, Moshkovitz, S
Book TitleGeological Society of America Special Papers
Pagination471–480
PublisherGeological Society of America
Abstract

The early Paleocene up to the initial establishment of stable oceanographie conditions after the K/T boundary event is examined in the eastern Tethys based on stratigraphie, faunal, CaCO3, and δ18O isotope analyses. The earliest Paleocene is characterized by redeposited and bioturbated sediments containing abundant reworked Cretaceous foraminifers and nannofossils mixed in with a characteristic basal Tertiary assemblage. Widespread hiatuses are identified in this interval based on abrupt truncation of dominant species and outcrop observations: at the K/T boundary, the P0/P1a boundary, and at the Pla/Plb boundary. Species diversity increases rapidly above this interval. These faunal changes are accompanied by decreasing CaCO3 accumulation interrupted by three major negative excursions: at the K/T boundary, in Subzone P1b, and at the P1b/P1c boundary coincident with deposition of a black organic-rich clay layer and the decline and eventual extinction of the dominant Cretaceous survivor Guembelitria. Stable-carbonate deposition began in foraminiferal Subzone P1c and the nannofossil NP1/NP2 Zone boundary about 400,000 years after the K/T boundary event, correlative with initial stabilization of foraminiferal assemblages as indicated by relatively stable species populations.   PDF

URLhttps://doi.org/10.1130/spe247-p471
DOI10.1130/spe247-p471
Original PublicationIn, Global Catastrophes in Earth History, Snowbird II

The Cretaceous/Tertiary boundary impact hypothesis and the paleontological record

TitleThe Cretaceous/Tertiary boundary impact hypothesis and the paleontological record
Publication TypeBook Chapter
Year of Publication1990
AuthorsKeller, G, Barrera, E
Book TitleGeological Society of America Special Papers
Pagination563–576
PublisherGeological Society of America
Abstract

Planktonic foraminifera show 30 to 45 percent of the species disappearing during the 300,000 to 400,000 years prior to the Cretaceous/Tertiary (K/T) boundary in continental shelf (El Kef, Tunisia) and epicontinental sea (Brazos River, Texas) sections. Their disappearance appears to be linked to a sea-level regression and global cooling. At the K/T boundary a 26 percent species reduction coincides with the geochemical anomalies at El Kef; their disappearance appears to be a direct consequence of the K/T boundary event. No change is observed at Brazos River. At both El Kef and Brazos River, many species (11 and 33 percent, respectively) disappear shortly after the K/T boundary, and all but one of the Cretaceous survivors terminally decline in relative abundance beginning at the K/T boundary. This pattern of species extinctions clearly shows a significant decline in species diversity during the latest Maastrichtian, followed by a sudden decline in diversity at the K/T boundary, which drastically and permanently altered planktonic foraminiferal communities. The K/T boundary event, however, did not cause instantaneous extinctions of nearly all species, as commonly claimed. Initial recovery of the ecosystem appears to have occurred about 230,000 years after the K/T boundary event, as implied by an increase in carbonate sedimentation, carbon isotope values, and diversification of planktonic foraminifera.

Carbon and oxygen isotope records of benthic and planktonic foraminifera at Brazos River reveal remarkable new data with far-reaching implications. For instance, the δ13C shift, which characterizes the K/T boundary globally, coincides with the micropaleontologically defined boundary and not with the tsunami deposit of Bourgeois and others (1988), indicating that the latter deposit is independent of the boundary event. Moreover, the δ13C shift occurs gradually over thousands of years, and not instantaneously as recorded in deep-sea sections, implying a more gradual and long-term effect than commonly assumed. Furthermore, stable isotopic data unequivocally show the survivorship of many Cretaceous species well into the early Tertiary.  PDF

URLhttps://doi.org/10.1130/spe247-p563
DOI10.1130/spe247-p563

Stable isotope evidence for gradual environmental changes and species survivorship across the Cretaceous/Tertiary Boundary

TitleStable isotope evidence for gradual environmental changes and species survivorship across the Cretaceous/Tertiary Boundary
Publication TypeJournal Article
Year of Publication1990
AuthorsBarrera, E, Keller, G
JournalPaleoceanography
Volume5
Pagination867–890
Date Published12/1990
Abstract

High-resolution δ13C and δ18O records have been generated from analyses of the planktonic foraminiferal species Heterohelix globulosa and the benthonic foraminiferal taxon Lenticulina spp from 3 m of a cored section spanning the Cretaceous/Tertiary (K/T) boundary at Brazos River, Texas. These are the first stable isotope records across the K/T boundary based on monospecific and monogeneric foraminiferal samples. They show a gradual decrease in δ13C values of about 2.5 permil beginning at the K/T boundary, as defined by the first appearance of Tertiary planktonic foraminifera, and continuing 17–20 cm above the boundary, approximately 40,000 years later. Gradual 13C depletion contrasts with the sudden δ13C drop at the K/T boundary observed in many deep-sea sections. The surface-to-bottom δ13C gradient decreased to less than zero approximately 25,000–30,000 years after the K/T boundary and remained negative for at least the next 140,000 years. Concomitant with change in δ13C values is a gradual decrease of about 2.5 permil in δ18C values which has not been observed at other localities. This 18O depletion suggests changes in temperature and/or salinity in the earliest Paleocene Gulf of Mexico. No extinction of foraminiferal species is associated with the K/T boundary or the onset of 18O and 13C depletions. Instead, two phases of Cretaceous species extinctions occur. One extinction phase is below the K/T boundary and below the tsunami bed of Bourgeois et al. [1988] and may be linked to sea level regression and environmental perturbations. The second extinction phase coincides with the minimum in δ13C and δ18O values in the Early Danian (Zone P0/Pla) and appears directly related to environmental changes reflected in the isotopic record. H. globulosa, which is commonly present in Maastrichtian and Danian sediments, exhibits significantly lower 18O/16O and 13C/12C ratios in Tertiary sediments relative to specimens from Maastrichtian sediments, demonstrating the survival of this important Cretaceous taxon after the K/T boundary event.  PDF

URLhttps://doi.org/10.1029/pa005i006p00867
DOI10.1029/pa005i006p00867

Extended period of extinctions across the Cretaceous /Tertiary boundary in planktonic foraminifera of continental-shelf sections: Implications for impact and volcanism theories

TitleExtended period of extinctions across the Cretaceous /Tertiary boundary in planktonic foraminifera of continental-shelf sections: Implications for impact and volcanism theories
Publication TypeJournal Article
Year of Publication1989
AuthorsKeller, G
JournalGeological Society of America Bulletin
Volume101
Pagination1408-1419
Abstract

The extinction of planktonic foraminiferal species across the Cretaceous/Tertiary (K/T) boundary has been examined in continental-shelf sections at El Kef, Tunisia, and Brazos River, Texas. These sections are considered to contain the most complete boundary transition record known to date. In both sections, an extended period of species extinctions spans from about 300,000 yr below to about 200,000-300,000 yr above the K/T boundary. Distinct episodes of accelerated extinctions occur below the boundary and about 50,000 yr above the boundary. At El Kef, only 26% of the species extinctions appear directly associated with the K/T boundary and iridium anomaly. At Brazos River, no species extinctions or measurable faunal changes appear directly associated with the K/T boundary and iridium anomaly. Species extinctions selectively affect large, ornate, tropical to subtropical species first and small, primitive, nonornate, subtropical to temperate species last. This pattern of species extinction is likely caused by increased ecological stresses as a result of a late Maastrichtian sea-level regression and global cooling. The extended period of species extinctions and absence of extinctions at the K/T boundary at Brazos River is not entirely compatible with either impact or volcanism theories. Perhaps, multiple unrelated causes should be considered, including a sea-level regression, global cooling, a K/T boundary impact of limited extent, and extensive volcanism.  PDF

URLhttp://gsabulletin.gsapubs.org/content/101/11/1408.abstract
DOI10.1130/0016-7606(1989)101<1408:EPOEAT>2.3.CO;2

Stable isotope, TOC and CaCO3 record across the cretaceous/tertiary boundary at El Kef, Tunisia

TitleStable isotope, TOC and CaCO3 record across the cretaceous/tertiary boundary at El Kef, Tunisia
Publication TypeJournal Article
Year of Publication1989
AuthorsKeller, G, Lindinger, M
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume73
Pagination243–265
Date Published10/2017
Abstract

We report the results of stable oxygen and carbon isotope analysis of carbonate fine fraction and benthic and planktic foraminifers, %CaCO3 and TOC determinations of sediments across the Cretaceous/Tertiary (K/T) boundary at El Kef, Tunisia. We used grain-size analysis of the fine fraction carbonate to determine possible compositional effects and smearslide and scanning electron microscope examinations to evaluate possible diagenetic alteration and microfossil preservation. The data suggests the following sequence of events.

Upper Maastrichtian oxygen and carbon isotope signals indicate relatively warm temperatures, a decreasing thermal gradient possibly related to a shallowing sea and relatively high surface water productivity. A sharp cooling appears to begin just below the K/T boundary. The K/T boundary is characterized by a sudden 2‰ negative shift in fine fraction δ13C, a slight 0.6‰ enrichment in benthic δ13C and a reduction of about 40% in CaCO3 sedimentation. These data imply strongly reduced surface water productivity as also observed in numerous deep-sea sequences worldwide. The lower Danian (planktic foraminiferal Zones P0,P1a) is marked by generally low productivity and unstable environmental conditions as indicated by generally low but fluctuating fine fraction δ13C values and low (5–15%) carbonate deposition. At the base of Subzone P1b, %CaCO3, benthic and fine fraction δ13C values increase gradually, and reach near pre-K/T boundary levels in Subzone P1c indicating initial recovery after the K/T boundary event about 300,000–400,000 years after the K/T boundary. The prolonged low productivity episode after the K/T crisis and the pre-K/T boundary cooling associated with a major reduction in planktic foraminiferal diversity are difficult to explain by a single K/T boundary bolide impact.  PDF

URLhttps://doi.org/10.1016/0031-0182(89)90007-2
DOI10.1016/0031-0182(89)90007-2

Extended Cretaceous/Tertiary boundary extinctions and delayed population change in planktonic foraminifera from Brazos River, Texas

TitleExtended Cretaceous/Tertiary boundary extinctions and delayed population change in planktonic foraminifera from Brazos River, Texas
Publication TypeJournal Article
Year of Publication1989
AuthorsKeller, G
JournalPaleoceanography
Volume4
Pagination287–332
Date Published06/1989
Abstract

High-resolution planktonic foraminiferal analysis of three Brazos River sections indicates a nearly continuous Cretaceous/Tertiary [K/T] boundary sedimentary record second only to the world's most complete record at El Kef, Tunisia. Species extinctions occur over an extended period of time and with two major extinction episodes. The first extinction episode with 46% of the species extinct occurs at and just below [10–15 cm] a short hiatus at the base of a sandy shell hash and clay-sand unit which was interpreted by Bourgeois et al. [1988] to represent a tsunami bed generated by the K/T boundary bolide impact. The top of this tsunami bed is about 17–20 cm below the K/T boundary as defined by the first appearance of Tertiary planktonic foraminifera. The second extinction phase with 45% of the species extinct occurs 25 cm above the K/T boundary [Zone P0/P1a boundary]. Of the remaining seven surviving Cretaceous species, six gradually disappear during planktonic foraminiferal Subzones P1a and basal P1b. No species extinctions or major faunal assemblage changes are directly associated with the K/T boundary. Iridium distribution is ambiguous, with one peak in the upper part of the tsunami bed and a second peak at the micropaleontologically defined K/T boundary. Relative abundances of dominant species are stable through the Late Maastrichtian, and only minor abundance changes coincide with the first extinction episode or the K/T boundary. The first major faunal change in the dominant species group coincides with the second extinction episode and leads to decline and eventual extinction of this group in Subzone P1a. Species disappearing at the two extinction episodes [46% and 45%] constitute only a small percentage [8% and 5%] of the individuals of the total planktonic foraminiferal population. This suggests that weakened species with low numbers of individuals and sensitive to relatively minor environmental changes were primarily affected by these extinction episodes. Magnetostratigraphy indicates that the first extinction phase began about 310,000 years before the K/T boundary, and the second extinction phase occurred 50,000 years after the K/T boundary. This stepped pattern of species extinctions suggests a progressively stressed ecosystem in continental shelf settings which may be related to an observed sea level regression and global cooling. The hypothesis of a global catastrophic mass extinction at the K/T boundary caused by a large extraterrestrial impact is not supported by the Brazos River planktonic foraminiferal data.  PDF

URLhttps://doi.org/10.1029/pa004i003p00287
DOI10.1029/pa004i003p00287

Extinction, survivorship and evolution of planktic foraminifera across the Cretaceous/Tertiary boundary at El Kef, Tunisia

TitleExtinction, survivorship and evolution of planktic foraminifera across the Cretaceous/Tertiary boundary at El Kef, Tunisia
Publication TypeJournal Article
Year of Publication1988
AuthorsKeller, G
JournalMarine Micropaleontology
Volume13
Issue3
Pagination239 - 263
Date PublishedJan-10-1988
ISSN03778398
Keywordsmass extinction
Abstract

An expanded sediment record at E1 Kef shows that the K/T boundary extinctions of planktic foraminifera extend over an interval from 25 cm below the geochemical boundary (Ir anomaly) to 7 cm above. Species extinctions appear sequential with complex, large, ornate forms disappearing first and smaller, less ornate, forms surviving longer. The 14 species extinctions below the boundary appear unrelated to an impact event.

Cretaceous species survivorship is greater than previously assumed. About 10 species survive (22%) into Subzone Pla (Globigerina eugubina). All Cretaceous survivors are small primitive forms which are generally smaller than their ancestors in Cretaceous sediments.

Species evolution after the K/T event occurs in two pulses. The first new Paleocene species evolve in the basal black clay (Zone PO ) immediately after the major Cretaceous extinctions. Evolving species are small and primitive similar to Cretaceous survivors. The second pulse in species evolution occurs in the lower part of Subzone Plb with the appearance of larger more diverse species. The first major increase in carbonate sedimentation and productivity occurs at this time and signals the recoveyr of the ecosystem nearly 300,000 years after the K/T event. The species extinctions prior to the generally assumed impact event implied by the Ir anomaly, and the long recovery period of the ecosystem thereafter cannot be explained by a single impact, but suggest that multiple causes may be responsible such as climatic changes, volcanism, a sea level drop, production of warm saline bottom water and the chemical consequences associated with increased salinity.  PDF

URLhttp://linkinghub.elsevier.com/retrieve/pii/0377839888900059
DOI10.1016/0377-8398(88)90005-9
Short TitleMarine Micropaleontology

Biotic turnover in benthic foraminifera across the cretaceous/tertiary boundary at El Kef, Tunisia

TitleBiotic turnover in benthic foraminifera across the cretaceous/tertiary boundary at El Kef, Tunisia
Publication TypeJournal Article
Year of Publication1988
AuthorsKeller, G
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume66
Pagination153–171
Date Publishedaug
Abstract

The Cretaceous/Tertiary boundary section exposed near El Kef, Tunisia is the most complete boundary sequence known to date. It contains nearly 1 m of black and gray boundary clay containing planktic foraminiferal Zone POa, b, 2 m of clayey shales of P1a (Globigerina eugubina) Zone and 4 m of shales and marls of P1b (G. taurica) Zone. Quantitative analysis of the benthic foraminiferal fauna suggests that deposition during the latest Cretaceous occurred in an upper slope to outer shelf environment which shallowed at the K/T boundary to an outer to middle shelf depth and shallowed further by P1b time to mid-shelf depth. A major reduction in benthic diversity occurred near the K/T boundary with about 50% of the fauna disappearing. Diversity remained an average of 37% lower during deposition of the first 3 m of sediment above the boundary (POa, b-P1a) and productivity was very low. Surviving and thriving foraminifers during this interval were primarily low oxygen tolerant epifaunal and infaunal species. A sharp decrease in the low oxygen tolerant fauna and appearance of a shallow mid-shelf fauna at about 4 m above the boundary (P1b Zone) signals a second regression, return to higher oxygen levels and higher productivity. Although the environmental effects of the K/T boundary event can be inferred from benthic faunas, the ultimate cause remains elusive. Faunal changes prior to and the long recovery period after the K/T boundary are difficult to explain by a single impact hypothesis.   PDF

URLhttps://doi.org/10.1016/0031-0182(88)90198-8
DOI10.1016/0031-0182(88)90198-8